UNIT-III

DESIGN ENGINEERING

Design Engineering: Design process and design quality, design concepts, the design model.
Creating an architectural design: software architecture, data design, architectural styles and
patterns, architectural design, conceptual model of UML, basic structural modeling, class
diagrams, sequence diagrams, collaboration diagrams, use case diagrams, component
diagrams.

Design engineering encompasses the set of principals, concepts, and practices that lead to
the development of a high- quality system or product.
✓ Design principles establish an overriding philosophy that guides the designer in the work that
is performed.
✓ Design concepts must be understood before the mechanics of design practice are applied
and
✓ Design practice itself leads to the creation of various representations of the software that
serve as a guide for the construction activity that follows.

What is design:
Design is what virtually every engineer wants to do. It is the place where creativity rules –
customer’s requirements, business needs, and technical considerations all come together in the
formulation of a product or a system. Design creates a representation or model of the software, but
unlike the analysis model, the design model provides detail about software data structures,
architecture, interfaces, and components that are necessary to implement the system.

Why is it important:
Design allows a software engineer to model the system or product that Is to be built. This model
can be assessed for quality and improved before code is generated, tests are conducted, and end –
users become involved in large numbers. Design is the place where software quality is established.

The goal of design engineering is to produce a model or representation that exhibits firmness,
commodity, and delight. To accomplish this, a designer must practice diversification and then
convergence. Another goal of software design is to derive an architectural rendering of a system.
The rendering serves as a framework from which more detailed design activities are conducted.
 1) DESIGN PROCESS AND DESIGN QUALITY:
Software design is an iterative process through which requirements are translated into a
“blueprint” for constructing the software.

Goals of design:
McGlaughlin suggests three characteristics that serve as a guide for the evaluation of a good design.
➢ The design must implement all of the explicit requirements contained in the analysis model,
and it must accommodate all of the implicit requirements desired by the customer.
➢ The design must be a readable, understandable guide for those who generate code and for
those who test and subsequently support the software.
➢ The design should provide a complete picture of the software, addressing the data,
functional, and behavioral domains from an implementation perspective.
Quality guidelines:
In order to evaluate the quality of a design representation we must establish technical criteria for
good design. These are the following guidelines:
1. A design should exhibit an architecture that
a. has been created using recognizable architectural styles or patterns
b. is composed of components that exhibit good design characteristics and
c. can be implemented in an evolutionary fashion, thereby facilitating implementation
and testing.
2. A design should be modular; that is, the software should be logically partitioned into elements
or subsystems.
3. A design should contain distinct representation of data, architecture, interfaces and
components.
4. A design should lead to data structures that are appropriate for the classes to be
implemented and are drawn from recognizable data patterns.
5. A design should lead to components that exhibit independent functional characteristics.
6. A design should lead to interface that reduce the complexity of connections between
components and with the external environment.
7. A design should be derived using a repeatable method that is driven by information obtained
during software requirements analysis.
8. A design should be represented using a notation that effectively communication its meaning.

These design guidelines are not achieved by chance. Design engineering encourages good design
through the application of fundamental design principles, systematic methodology, and thorough
review.
Quality attributes:
The FURPS quality attributes represent a target for all software design:
➢ Functionality is assessed by evaluating the feature set and capabilities of the program, the
generality of the functions that are delivered, and the security of the overall system.
➢ Usability is assessed by considering human factors, overall aesthetics, consistency and
documentation.
➢ Reliability is evaluated by measuring the frequency and severity of failure, the accuracy of
output results, and the mean – time –to- failure (MTTF), the ability to recover from failure,
and the predictability of the program.
➢ Performance is measured by processing speed, response time, resource consumption,
throughput, and efficiency
➢ Supportability combines the ability to extend the program (extensibility), adaptability,
serviceability- these three attributes represent a more common term maintainability
Not every software quality attribute is weighted equally as the software design is developed. One
application may stress functionality with a special emphasis on security.
Another may demand performance with particular emphasis on processing speed.
A third might focus on reliability.

2) DESIGN CONCEPTS:

M.A Jackson once said:”The beginning of wisdom for a software engineer is to recognize the
difference between getting a program to work, and getting it right.” Fundamental software design
concepts provide the necessary framework for “getting it right.”

I. Abstraction: Many levels of abstraction are there.

✓ At the highest level of abstraction, a solution is stated in broad terms using the language of
the problem environment.
✓ At lower levels of abstraction, a more detailed description of the solution is provided.
A procedural abstraction refers to a sequence of instructions that have a specific and limited
function. The name of procedural abstraction implies these functions, but specific details are
suppressed.
A data abstraction is a named collection of data that describes a data object.
In the context of the procedural abstraction open, we can define a data abstraction called door. Like
any data object, the data abstraction for door would encompass a set of attributes that describe the
door (e.g., door type, swing operation, opening mechanism, weight, dimensions). It follows that the
procedural abstraction open would make use of information contained in the attributes of the data
abstraction door.
 II. Architecture:
Software architecture alludes to “the overall structure of the software and the ways in which that
structure provides conceptual integrity for a system”. In its simplest form, architecture is the structure
or organization of program components (modules), the manner in which these components interact,
and the structure of data that are used by the components.
One goal of software design is to derive an architectural rendering of a system. The rendering serves
as a framework from which more detailed design activities are conducted.
The architectural design can be represented using one or more of a number of different models.
Structured models represent architecture as an organized collection of program components.
Framework models increase the level of design abstraction by attempting to identify repeatable
architectural design frameworks that are encountered in similar types of applications.
Dynamic models address the behavioral aspects of the program architecture, indicating how the
structure or system configuration may change as a function external events.
Process models focus on the design of the business or technical process that the system must
accommodate.
Functional models can be used to represent the functional hierarchy of a system.
III. Patterns:
Brad Appleton defines a design pattern in the following manner: “a pattern is a named nugget of
inside which conveys that essence of a proven solution to a recurring problem within a certain context
amidst competing concerns.” Stated in another way, a design pattern describes a design structure
that solves a particular design within a specific context and amid “forces” that may have an impact on
the manner in which the pattern is applied and used.
The intent of each design pattern is to provide a description that enables a designer to determine
1) Whether the pattern is capable to the current work,
2) Whether the pattern can be reused,
3) Whether the pattern can serve as a guide for developing a similar, but functionally or
structurally different pattern.
IV. Modularity:
Software architecture and design patterns embody modularity; software is divided into
separately named and addressable components, sometimes called modules that are integrated to
satisfy problem requirements.
It has been stated that “modularity is the single attribute of software that allows a program
to be intellectually manageable”. Monolithic software cannot be easily grasped by a software
engineer. The number of control paths, span of reference, number of variables, and overall
complexity would make understanding close to impossible.
The “divide and conquer” strategy- it’s easier to solve a complex problem when you break it
into manageable pieces. This has important implications with regard to modularity and software. If we
 subdivide software indefinitely, the effort required to develop it will become negligibly small. The effort
to develop an individual software module does decrease as the total number of modules increases.
Given the same set of requirements, more modules means smaller individual size. However, as the
number of modules grows, the effort associated with integrating the modules also grow.
Under modularity or over modularity should be avoided. We modularize a design so that
development can be more easily planned; software increment can be defined and delivered;
chamges can be more easily accommodated; testing and debugging can be conducted more
efficiently, and long-term maintenance can be conducted without serious side effects.
V. Information Hiding:
The principle of information hiding suggests that modules be “characterized by design decision
that hides from all others.”
Modules should be specified and designed so that information contained within a module is
inaccessible to other modules that have no need for such information.
Hiding implies that effective modularity can be achieved by defining a set of independent
modules that communicate with one another only that information necessary to achieve software
function. Abstraction helps to define the procedural entities that make up the software. Hiding defines
and enforces access constraints to both procedural detail within a module and local data structure
used by module.
The use of information hiding as a design criterion for modular systems provides the greatest
benefits when modifications are required during testing and later, during software maintenance.
Because most data and procedure are hidden from other parts of the software, inadvertent errors
introduced during modification are less likely to propagate to other locations within software.
VI. Functional Independence:
The concept of functional independence is a direct outgrowth of modularity and the
concepts of abstraction and information hiding. Functional independence is achieved by developing
modules with “single minded” function and an “aversion” to excessive interaction with other modules.
Stated another way, we want to design software so that each module addresses a specific sub
function of requirements and has a simple interface when viewed from other parts of the program
structure.
Software with effective modularity, that is, independent modules, is easier to develop
because function may be compartmentalized and interfaces are simplified. Independent sign or code
modifications are limited, error propagation is reduced, and reusable modules are possible. To
summarize, functional independence is a key to good design, and design is the key to software
quality.
Independence is assessed using two qualitative criteria: cohesion and coupling. Cohesion is
an indication of the relative functional strength of a module. Coupling is an indication of the relative
interdependence among modules. Cohesion is a natural extension of the information hiding.
 A cohesion module performs a single task, requiring little interaction with other components
in other parts of a program. Stated simply, a cohesive module should do just one thing.
Coupling is an indication of interconnection among modules in a software structure.
Coupling depends on the interface complexity between modules, the point at which entry or reference
is made to a module, and what data pass across the interface. In software design, we strive for
lowest possible coupling. Simple connectivity among modules results in software that is easier to
understand and less prone to a “ripple effect”, caused when errors occur at one location and
propagates throughout a system.
VII. Refinement:
Stepwise refinement is a top- down design strategy originally proposed by Niklaus wirth. A
program is development by successively refining levels of procedural detail. A hierarchy is
development by decomposing a macroscopic statement of function in a step wise fashion until
programming language statements are reached.
Refinement is actually a process of elaboration. We begin with a statement of function that is
defined at a high level of abstraction. That is, the statement describes function or information
conceptually but provides no information about the internal workings of the function or the internal
structure of the data. Refinement causes the designer to elaborate on the original statement,
providing more and more detail as each successive refinement occurs.
Abstraction and refinement are complementary concepts. Abstraction enables a designer to
specify procedure and data and yet suppress low-level details. Refinement helps the designer to
reveal low-level details as design progresses. Both concepts aid the designer in creating a complete
design model as the design evolves.

VIII. Refactoring:
Refactoring is a reorganization technique that simplifies the design of a component without
changing its function or behavior. Fowler defines refactoring in the following manner: “refactoring is
the process of changing a software system in such a way that it does not alter the external behavior
of the code yet improves its internal structure.”
When software is refactored, the existing design is examined for redundancy, unused design
elements, inefficient or unnecessary algorithms, poorly constructed or inappropriate data structures,
or any other design failure that can be corrected to yield a better design. The designer may decide
that the component should be refactored into 3 separate components, each exhibiting high cohesion.
The result will be software that is easier to integrate, easier to test, and easier to maintain.
IX. Design classes:
The software team must define a set of design classes that
1. Refine the analysis classes by providing design detail that will enable the classes to be
implemented, and
 2. Create a new set of design classes that implement a software infrastructure to support the
design solution.
Five different types of design classes, each representing a different layer of the design architecture
are suggested.
➢ User interface classes: define all abstractions that are necessary for human computer
interaction. In many cases, HCL occurs within the context of a metaphor and the design
classes for the interface may be visual representations of the elements of the metaphor.
➢ Business domain classes: are often refinements of the analysis classes defined earlier.
The classes identify the attributes and services that are required to implement some element
of the business domain.
➢ Process classes implement lower – level business abstractions required to fully manage the
business domain classes.
➢ Persistent classes represent data stores that will persist beyond the execution of the
software.
➢ System classes implement software management and control functions that enable the
system to operate and communicate within its computing environment and with the outside
world.
As the design model evolves, the software team must develop a complete set of
attributes and operations for each design class. The level of abstraction is reduced as each analysis
class is transformed into a design representation. Each design class be reviewed to ensure that it is
“well-formed.” They define four characteristics of a well- formed design class.

Complete and sufficient: A design class should be the complete encapsulation of all attributes and
methods that can reasonably be expected to exist for the class. Sufficiency ensures that the design
class contains only those methods that are sufficient to achieve the intent of the class, no more and
no less.

Primitiveness: Methods associated with a design class should be focused on accomplishing one
service for the class. Once the service has been implemented with a method, the class should not
provide another way to accomplish the same thing.

High cohesion: A cohesive design class has a small, focused set of responsibilities and single-
mindedly applies attributes and methods to implement those responsibilities.

Low coupling: Within the design model, it is necessary for design classes to collaborate with one
another. However, collaboration should be kept to an acceptable minimum. If a design model is
highly coupled the system is difficult to implement, to test, and to maintain over time. In general,
design classes within a subsystem should have only limited knowledge of classes in other
 subsystems. This restriction, called the law of Demeter, suggests that a method should only sent
messages to methods in neighboring classes.

THE DESIGN MODEL:

• The design model can be viewed into different dimensions.
• The process dimension indicates the evolution of the design model as design tasks are
executed as a part of the software process.
The abstraction dimension represents the level of detail as each element of the analysis model is
transformed into a design equivalent and then refined iteratively.
The elements of the design model use many of the same UML diagrams that were used in the
analysis model. The difference is that these diagrams are refined and elaborated as a path of design;
more implementation- specific detail is provided, and architectural structure and style, components
that reside within the architecture, and the interface between the components and with the outside
world are all emphasized.
It is important to mention however, that model elements noted along the horizontal axis are
not always developed in a sequential fashion. In most cases preliminary architectural design sets the
stage and is followed by interface design and component-level design, which often occur in parallel.
The deployment model us usually delayed until the design has been fully developed.
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Process Dimension
Data design elements:
Data design sometimes referred to as data architecting creates a model of data and/or information
that is represented at a high level of abstraction. This data model is then refined into progressively
more implementation-specific representations that can be processed by the computer-based system.
The structure of data has always been an important part of software design.

✓ At the program component level, the design of data structures and the associated
algorithms required to manipulate them is essential to the criterion of high-quality
applications.
✓ At the application level, the translation of a data model into a database is pivotal to
achieving the business objectives of a system.
✓ At the business level, the collection of information stored in disparate databases and
reorganized into a “data warehouse” enables data mining or knowledge discovery that can
have an impact on the success of the business itself.

i. Architectural design elements:

The architectural design for software is the equivalent to the floor plan of a house. The
architectural model is derived from three sources.
1) Information about the application domain for the software to be built.
2) Specific analysis model elements such as data flow diagrams or analysis classes,
their relationships and collaborations for the problem at hand, and
3) The availability of architectural patterns

ii. Interface design elements:

The interface design for software is the equivalent to a set of detailed drawings for the doors,
windows, and external utilities of a house.
The interface design elements for software tell how information flows into and out of the
system and how it is communicated among the components defined as part of the
architecture. There are 3 important elements of interface design:
1) The user interface(UI);
2) External interfaces to other systems, devices, networks, or other produces or
consumers of information; and
3) Internal interfaces between various design components.
These interface design elements allow the software to communicated externally and enable
internal communication and collaboration among the components that populate the software
architecture.
 UI design is a major software engineering action.

The design of a UI incorporates aesthetic elements (e.g., layout, color, graphics, interaction
mechanisms), ergonomic elements (e.g., information layout and placement, metaphors, UI
navigation), and technical elements (e.g., UI patterns, reusable components). In general, the UI is a
unique subsystem within the overall application architecture.
The design of external interfaces requires definitive information about the entity to which
information is sent or received. The design of external interfaces should incorporate error checking
and appropriated security features.
UML defines an interface in the following manner:”an interface is a specifier for the
externally- visible operations of a class, component, or other classifier without specification of internal
structure.”

iii. Component- level design elements: The component-level design for software is equivalent
to a set of detailed drawings.
The component-level design for software fully describes the internal detail of each software
component. To accomplish this, the component-level design defines data structures for all
local data objects and algorithmic detail for all processing that occurs within a component
and an interface that allows access to all component operations.

SensorMana
gement Sensor

iv. Deployment-level design elements: Deployment-level design elements indicated how

software functionality and subsystems will be allocated within the physical computing
environment that will support the software
 Cont rol CPI serv
Panel er
Security homeownerAcces
s

Personal comput
er
externalAccess

Security Surveillance

homeManagemen communication
t

Figure 9 . 8 UML deploy m ent diagram for SafeHom e

ARCHITECTURAL DESIGN
1) SOFTWARE ARCHITECTURE: What Is Architecture?
Architectural design represents the structure of data and program components that are
required to build a computer-based system. It considers
- the architectural style that the system will take,
- the structure and properties of the components that constitute the system, and
- the interrelationships that occur among all architectural components of a system.

The architecture is a representation that enables a software engineer to

(1) analyze the effectiveness of the design in meeting its stated requirements,
(2) consider architectural alternatives at a stage when making design changes is still
relatively easy,
(3) reducing the risks associated with the construction of the software.

The design of software architecture considers two levels of the design pyramid
- data design
- architectural design.
✓ Data design enables us to represent the data component of the architecture.
✓ Architectural design focuses on the representation of the structure of software components,
their properties, and interactions.
Why Is Architecture Important?
Bass and his colleagues [BAS98] identify three key reasons that software architecture is important:
• Representations of software architecture are an enabler for communication between all
parties (stakeholders) interested in the development of a computer-based system.
• The architecture highlights early design decisions that will have a profound impact on all
software engineering work that follows and, as important, on the ultimate success of the
system as an operational entity.
• Architecture “constitutes a relatively small, intellectually graspable model of how the system is
structured and how its components work together”

2) DATA DESIGN:
The data design activity translates data objects as part of the analysis model into data
structures at the software component level and, when necessary, a database architecture at the
application level.
➢ At the program component level, the design of data structures and the associated algorithms
required to manipulate them is essential to the creation of high-quality applications.
➢ At the application level, the translation of a data model (derived as part of requirements
engineering) into a database is pivotal to achieving the business objectives of a system.
➢ At the business level, the collection of information stored in disparate databases and
reorganized into a “data warehouse” enables data mining or knowledge discovery that can
have an impact on the success of the business itself.

Data design at the Architectural Level:

The challenge for a business has been to extract useful information from this data environment,
particularly when the information desired is cross functional.

To solve this challenge, the business IT community has developed data mining techniques,
also called knowledge discovery in databases (KDD), that navigate through existing databases in
an attempt to extract appropriate business-level information. An alternative solution, called a data
warehouse, adds an additional layer to the data architecture. a data warehouse is a large,
independent database that encompasses some, but not all, of the data that are stored in databases
that serve the set of applications required by a business.

Data design at the Component Level:

Data design at the component level focuses on the representation of data structures that are
directly accessed by one or more software components. The following set of principles for data
specification:
 1. The systematic analysis principles applied to function and behavior should also be applied to
data.
2. All data structures and the operations to be performed on each should be identified.
3. A data dictionary should be established and used to define both data and program design.
4. Low-level data design decisions should be deferred until late in the design process.
5. The representation of data structure should be known only to those modules that must make
direct use of the data contained within the structure.
6. A library of useful data structures and the operations that may be applied to them should be
developed.
7. A software design and programming language should support the specification and
realization of abstract data types.
3) ARCHITECTURAL STYLES AND PATTERNS:
The builder has used an architectural style as a descriptive mechanism to differentiate the
house from other styles (e.g., A-frame, raised ranch, Cape Cod).
The software that is built for computer-based systems also exhibits one of many architectural
styles.
Each style describes a system category that encompasses
(1) A set of components (e.g., a database, computational modules) that perform a function
required by a system;
(2) A set of connectors that enable “communication, coordinations and cooperation” among
components;
(3) Constraints that define how components can be integrated to form the system; and
(4) Semantic models that enable a designer to understand the overall properties of a
system by analyzing the known properties of its constituent parts.
An architectural pattern, like an architectural style, imposes a transformation the design of
architecture. However, a pattern differs from a style in a number of fundamental ways:
(1) The scope of a pattern is less broad, focusing on one aspect of the architecture rather than
the architecture in its entirety.
(2) A pattern imposes a rule on the architecture, describing how the software will handle some
aspect of its functionality at the infrastructure level.
(3) Architectural patterns tend to address specific behavioral issues within the context of the
architectural.

A Brief Taxonomy of Styles and Patterns Data-centered architectures:

A data store (e.g., a file or database) resides at the center of this architecture and is
accessed frequently by other components that update, add, delete, or otherwise modify data within
the store. A variation on this approach transforms the repository into a “blackboard” that sends
notification to client software when data of interest to the client changes
Data-centered architectures promote integrability. That is, existing components can be
changed and new client components can be added to the architecture without concern about other
clients (because the client components operate independently). In addition, data can be passed
among clients using the blackboard mechanism

Data-flow architectures. This architecture is applied when input data are to be transformed through
a series of computational or manipulative components into output data. A pipe and filter pattern has
a set of components, called filters, connected by pipes that transmit data from one component to the
next. Each filter works independently of those components upstream and downstream, is designed to
expect data input of a certain form, and produces data output of a specified form.

If the data flow degenerates into a single line of transforms, it is termed batch sequential.
This pattern accepts a batch of data and then applies a series of sequential components (filters) to
transform it.
Call and return architectures. This architectural style enables a software designer (system
architect) to
achieve a program structure that is relatively easy to modify and scale. A number of substyles
[BAS98] exist within this category:
• Main program/subprogram architectures. This classic program structure decomposes
function into a control hierarchy where a “main” program invokes a number of program
components, which in turn may invoke still other components. Figure 13.3 illustrates an
architecture of this type.
• Remote procedure call architectures. The components of a main program/ subprogram
architecture are distributed across multiple computers on a network

Object-oriented architectures. The components of a system encapsulate data and the operations
that must be applied to manipulate the data. Communication and coordination between components
is accomplished via message passing.

Layered architectures. The basic structure of a layered architecture is illustrated in Figure 14.3. A
number of different layers are defined, each accomplishing operations that progressively become
closer to the machine instruction set. At the outer layer, components service user interface
operations. At the inner layer, components perform operating system interfacing. Intermediate layers
provide utility services and application software functions.
Architectural Patterns:
An architectural pattern, like an architectural style, imposes a transformation the design of
architecture. However, a pattern differs from a style in a number of fundamental ways:
(1) The scope of a pattern is less broad, focusing on one aspect of the architecture rather than
the architecture in its entirety.
(2) A pattern imposes a rule on the architecture, describing how the software will handle some
aspect of its functionality at the infrastructure level.
(3) Architectural patterns tend to address specific behavioral issues within the context of the
architectural.
The architectural patterns for software define a specific approach for handling some behavioral
characteristics of the system
Concurrency—applications must handle multiple tasks in a manner that simulates parallelism
o operating system process management pattern
o task scheduler pattern
Persistence—Data persists if it survives past the execution of the process that created it. Two
patterns are common:
• a database management system pattern that applies the storage and retrieval
capability of a DBMS to the application architecture
• an application level persistence pattern that builds persistence features into the
application architecture
Distribution— the manner in which systems or components within systems communicate with one
another in a distributed environment
 • A broker acts as a ‘middle-man’ between the client component and a server
component.
Organization and Refinement:
The design process often leaves a software engineer with a number of architectural alternatives, it is
important to establish a set of design criteria that can be used to assess an architectural design that
is derived. The following questions provide insight into the architectural style that has been derived:
Control.
✓ How is control managed within the architecture?
✓ Does a distinct control hierarchy exist, and if so, what is the role of components within this
control hierarchy?
✓ How do components transfer control within the system?
✓ How is control shared among components?
Data.
✓ How are data communicated between components?
✓ Is the flow of data continuous, or are data objects passed to the system sporadically?
✓ What is the mode of data transfer (i.e., are data passed from one component to another or
are data available globally to be shared among system components)?
✓ Do data components (e.g., a blackboard or repository) exist, and if so, what is their role?
✓ How do functional components interact with data components?
✓ Are data components passive or active (i.e., does the data component actively interact with
other components in the system)? How do data and control interact within the system?
4) ARCHITECTURAL DESIGN:
I Representing the System in Context:
At the architectural design level, a software architect uses an architectural context diagram (ACD)
to model the manner in which software interacts with entities external to its boundaries. The generic
structure of the architectural context diagram is illustrated in the figure
Superordinate systems
Safehome Internet-based
Product system

control
panel target system: surveillance
function
Security Function uses
homeowner
uses

uses

sensors sensors
peers

Superordinate systems – those systems that use the target system as part of some higher level
processing scheme.
Subordinate systems - those systems that are used by the target system and provide data or
processing that are necessary to complete target system functionality.

Peer-level systems - those systems that interact on a peer-to-peer basis

Actors -those entities that interact with the target system by producing or consuming information that
is necessary for requisite processing

II Defining Archetypes:
An archetype is a class or pattern that represents a core abstraction that is critical to the design
of architecture for the target system. In general, a relative small set of archetypes is required to
design even relatively complex systems.
In many cases, archetypes can be derived by examining the analysis classes defined as part of
the analysis model. In safe home security function, the following are the archetypes:
- Node: Represent a cohesive collection of input and output elements of the home security
function. For example a node might be comprised of (1) various sensors, and (2) a
variety of alarm indicators.
- Detector: An abstraction that encompasses all sensing equipment that feeds information
into the target system
- Indicator: An abstraction that represents all mechanisms for indication that an alarm
condition is occurring.
- Controller: An abstraction that depicts the mechanism that allows the arming or
disarming of a node. If controllers reside on a network, they have the ability to
communicate with one another.
 Figure 10.7 UML relat ionships for SafeHome security function archetypes (adapted f rom [ BOS00])

III Refining the Architecture into Components:

As the architecture is refined into components, the structure of the system begins to emerge. The
architectural designer begins with the classes that were described as part of the analysis model.
These analysis classes represent entities within the application domain that must be addressed
within the software architecture. Hence, the application domain is one source is the infrastructure
domain. The architecture must accommodate many infrastructure components that enable
application domain.

For eg: memory management components, communication components database components, and
task management components are often integrated into the software architecture.
In the safeHome security function example, we might define the set of top-level components that
address the following functionality:
• External communication management- coordinates communication of the security
function with external entities
• Control panel processing- manages all control panel functionality.
• Detector management- coordinates access to all detectors attached to the system.
• Alarm processing- verifies and acts on all alarm conditions.
Design classes would be defined for each. It is important to note, however, that the design details of
all attributes and operations would not be specified until component-level design.

SafeHome
Executive

Function
select ion

Ext ernal
Communicat ion
Management

Security Surveillance Home

management

GUI Internet
Interface
Cont rol panel det ect or
alarm
processing management
processing

Component Structure

IV Describing Instantiations of the System: An actual instantiation of the architecture means the
architecture is applied to a specific problem with the intent of demonstrating that the structure and
components are appropriate.

SafeHome
Execut ive

Ext ernal

Communicat ion
Management

Security

GUI Internet
Interface
Cont rol det ect or alarm
processing
panel m anagem ent
processing
Key pad
processing scheduler phone

com m unicat ion

CP display
funct ions alarm

sensor

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 Object And Object Classes
• Object : An object is an entity that has a state and a defined set of operations that operate on
that state.
• An obect class defination is both a type specification and a template for creating obects.
• It includes declaration of all the attributes and operations that are associated with object of
that class.
Object Oriented Design Process
• There are five stages of object oriented design process 1)Understand and define the
context and the modes of use of the system. 2)Design the system architecture
3)Identify the principle objects in the system. 4)Develop a design models
5) Specify the object interfaces Systems context and modes of use
• It specify the context of the system.it also specify the relationships between the software that
is being designed and its external environment.
• If the system context is a static model it describe the other system in that environment.
• If the system context is a dynamic model then it describe how the system actually interact with the
environment.System Architecture
• Once the interaction between the software system that being designed and the
system environment have been defined
• We can use the above information as basis for designing the System Architecture.
Object Identification
• This process is actually concerned with identifying the object classes.
• We can identify the object classes by the following 1)Use a grammatical analysis
2)Use a tangible entities 3)Use a behaviourial approach
4) Use a scenario based approach Design model
• Design models are the bridge between the requirements and implementation.
• There are two type of design models
1) Static model describe the relationship between the objects. 2)Dynamic model describe the
interaction between the objects
• Object Interface SpecificationIt is concerned with specifying the details of the
interfaces to an objects.
• Design evolution
The main advantage OOD approach is to simplify the problem of making changes to the
design. Changing the internal details of an obect is unlikely to effect any other system
object.
UML OVERVIEW
UML (Unified Modeling Language) is a standard language for specifying,
visualizing, constructing, and documenting the artifacts of software systems. UML was
created by the Object Management Group (OMG) and UML 1.0 specification draft was
proposed to the OMG in January 1997. It was initially started to capture the behavior of
complex software and non-software system and now it has become an OMG standard.
This tutorial gives a complete understanding on UML.

HISTORY
UML is a standard language for specifying, visualizing, constructing, and
documenting the artifacts of software systems.
UML was created by the Object Management Group (OMG) and UML 1.0 specification
draft was proposed to the OMG in January 1997.
OMG is continuously making efforts to create a truly industry standard.
• UML stands for Unified Modeling Language.
• UML is different from the other common programming languages such as C++,
Java, COBOL, etc.
• UML is a pictorial language used to make software blueprints.
• UML can be described as a general purpose visual modeling language to
visualize, specify, construct, and document software system.
• Although UML is generally used to model software systems, it is not limited within
this boundary. It is also used to model non-software systems as well. For
example, the process flow in a manufacturing unit, etc.
UML is not a programming language but tools can be used to generate code in various
languages using UML diagrams. UML has a direct relation with object oriented analysis
and design. After some standardization, UML has become an OMG standard.
Goals of UML
A picture is worth a thousand words, this idiom absolutely fits describing UML.
Object-oriented concepts were introduced much earlier than UML. At that point of time,
there were no standard methodologies to organize and consolidate the object-oriented
development. It was then that UML came into picture.
There are a number of goals for developing UML but the most important is to
define some general purpose modeling language, which all modelers can use and it
also needs to be made simple to understand and use.
UML diagrams are not only made for developers but also for business users,
common people, and anybody interested to understand the system. The system can be
a software or non-software system. Thus it must be clear that UML is not a
development method rather it accompanies with processes to make it a successful
system.
In conclusion, the goal of UML can be defined as a simple modeling mechanism
to model all possible practical systems in today’s complex environment.

A Conceptual Model of UML

To understand the conceptual model of UML, first we need to clarify what is a
conceptual model? and why a conceptual model is required?
• A conceptual model can be defined as a model which is made of concepts and
their relationships.
• A conceptual model is the first step before drawing a UML diagram. It helps to
understand the entities in the real world and how they interact with each other.
As UML describes the real-time systems, it is very important to make a conceptual
model and then proceed gradually. The conceptual model of UML can be mastered by
learning the following three major elements −
• UML building blocks
• Rules to connect the building blocks
• Common mechanisms of UML
Object-Oriented Concepts
UML can be described as the successor of object-oriented (OO) analysis and
design.
An object contains both data and methods that control the data. The data
represents the state of the object. A class describes an object and they also form a
hierarchy to model the real-world system. The hierarchy is represented as inheritance
and the classes can also be associated in different ways as per the requirement.
Objects are the real-world entities that exist around us and the basic concepts such as
abstraction, encapsulation, inheritance, and polymorphism all can be represented using
UML.
UML is powerful enough to represent all the concepts that exist in object-oriented
analysis and design. UML diagrams are representation of object-oriented concepts
only. Thus, before learning UML, it becomes important to understand OO concept in
detail.

Following are some fundamental concepts of the object-oriented world −

• Objects − Objects represent an entity and the basic building block.
• Class − Class is the blue print of an object.
• Abstraction − Abstraction represents the behavior of an real world entity.
• Encapsulation − Encapsulation is the mechanism of binding the data together
and hiding them from the outside world.
• Inheritance − Inheritance is the mechanism of making new classes from existing
ones.
• Polymorphism − It defines the mechanism to exists in different forms.

OO Analysis and Design

OO can be defined as an investigation and to be more specific, it is the
investigation of objects. Design means collaboration of identified objects.
Thus, it is important to understand the OO analysis and design concepts. The most
important purpose of OO analysis is to identify objects of a system to be designed. This
analysis is also done for an existing system. Now an efficient analysis is only possible
when we are able to start thinking in a way where objects can be identified. After
identifying the objects, their relationships are identified and finally the design is
produced.

The purpose of OO analysis and design can described as −

• Identifying the objects of a system.
• Identifying their relationships.
• Making a design, which can be converted to executables using OO languages.
There are three basic steps where the OO concepts are applied and implemented. The
steps can be defined as
OO Analysis → OO Design → OO implementation using OO languages

The above three points can be described in detail as −

• During OO analysis, the most important purpose is to identify objects and
describe them in a proper way. If these objects are identified efficiently, then the
next job of design is easy. The objects should be identified with responsibilities.
Responsibilities are the functions performed by the object. Each and every
object has some type of responsibilities to be performed. When these
responsibilities are collaborated, the purpose of the system is fulfilled.
• The second phase is OO design. During this phase, emphasis is placed on the
requirements and their fulfilment. In this stage, the objects are collaborated
according to their intended association. After the association is complete, the
design is also complete.
• The third phase is OO implementation. In this phase, the design is implemented
using OO languages such as Java, C++, etc.

Role of UML in OO Design

UML is a modeling language used to model software and non-software systems.
Although UML is used for non-software systems, the emphasis is on modeling OO
software applications. Most of the UML diagrams discussed so far are used to model
different aspects such as static, dynamic, etc. Now whatever be the aspect, the artifacts
are nothing but objects.
If we look into class diagram, object diagram, collaboration diagram, interaction
diagrams all would basically be designed based on the objects.
Hence, the relation between OO design and UML is very important to understand. The
OO design is transformed into UML diagrams according to the requirement. Before
understanding the UML in detail, the OO concept should be learned properly. Once the
OO analysis and design is done, the next step is very easy. The input from OO analysis
and design is the input to UML diagrams.

UML - Building Blocks

As UML describes the real-time systems, it is very important to make a conceptual
model and then proceed gradually. The conceptual model of UML can be mastered by
learning the following three major elements −
• UML building blocks
• Rules to connect the building blocks
• Common mechanisms of UML
This chapter describes all the UML building blocks. The building blocks of UML can be
defined as −
• Things
• Relationships
• Diagrams

Things
Things are the most important building blocks of UML. Things can be −
• Structural
• Behavioral
• Grouping
• Annotational
Structural Things
Structural things define the static part of the model. They represent the physical and
conceptual elements. Following are the brief descriptions of the structural things.
Class − Class represents a set of objects having similar responsibilities.

Interface − Interface defines a set of operations, which specify the responsibility of a

class.

Collaboration −Collaboration defines an interaction between elements.

Use case −Use case represents a set of actions performed by a system for a specific
goal.

Component −Component describes the physical part of a system.

Node − A node can be defined as a physical element that exists at run time.
Behavioral Things
A behavioral thing consists of the dynamic parts of UML models. Following are the
behavioral things −
Interaction − Interaction is defined as a behavior that consists of a group of messages
exchanged among elements to accomplish a specific task.

State machine − State machine is useful when the state of an object in its life cycle is
important. It defines the sequence of states an object goes through in response to
events. Events are external factors responsible for state change

Grouping Things
Grouping things can be defined as a mechanism to group elements of a UML model
together. There is only one grouping thing available −
Package − Package is the only one grouping thing available for gathering structural
and behavioral things.

Annotational Things
Annotational things can be defined as a mechanism to capture remarks, descriptions,
and comments of UML model elements. Note - It is the only one Annotational thing
available. A note is used to render comments, constraints, etc. of an UML element.
Relationship
Relationship is another most important building block of UML. It shows how the
elements are associated with each other and this association describes the functionality
of an application.
There are four kinds of relationships available.
Dependency
Dependency is a relationship between two things in which change in one element also
affects the other.

Association
Association is basically a set of links that connects the elements of a UML model. It
also describes how many objects are taking part in that relationship.

Generalization
Generalization can be defined as a relationship which connects a specialized element
with a generalized element. It basically describes the inheritance relationship in the
world of objects.

Realization
Realization can be defined as a relationship in which two elements are connected. One
element describes some responsibility, which is not implemented and the other one
implements them. This relationship exists in case of interfaces.
UML Diagrams
UML diagrams are the ultimate output of the entire discussion. All the elements,
relationships are used to make a complete UML diagram and the diagram represents a
system.
The visual effect of the UML diagram is the most important part of the entire process.
All the other elements are used to make it complete.
UML includes the following nine diagrams, the details of which are described in the
subsequent chapters.
• Class diagram
• Object diagram
• Use case diagram
• Sequence diagram
• Collaboration diagram
• Activity diagram
• Statechart diagram
• Deployment diagram
• Component diagram

UML - Modeling Types

It is very important to distinguish between the UML model. Different diagrams are
used for different types of UML modeling. There are three important types of UML
modeling.

Structural Modeling
Structural modeling captures the static features of a system. They consist of the
following −
1) Classes diagrams 2) Objects diagrams
3 Deployment diagrams 4 Package diagrams
5) Composite structure diagram 6) Component diagram
Structural model represents the framework for the system and this framework is the
place where all other components exist. Hence, the class diagram, component diagram
and deployment diagrams are part of structural modeling. They all represent the
elements and the mechanism to assemble them.
The structural model never describes the dynamic behavior of the system. Class
diagram is the most widely used structural diagram.

Behavioral Modeling
Behavioral model describes the interaction in the system. It represents the interaction
among the structural diagrams. Behavioral modeling shows the dynamic nature of the
system. They consist of the following −
• Activity diagrams
• Interaction diagrams
• Use case diagrams
All the above show the dynamic sequence of flow in a system.

Architectural Modeling
Architectural model represents the overall framework of the system. It contains both
structural and behavioral elements of the system. Architectural model can be defined as
the blueprint of the entire system. Package diagram comes under architectural
modeling

UML - Basic Notations

UML is popular for its diagrammatic notations. We all know that UML is for
visualizing, specifying, constructing and documenting the components of software and
non-software systems. Hence, visualization is the most important part which needs to
be understood and remembered.
UML notations are the most important elements in modeling. Efficient and
appropriate use of notations is very important for making a complete and meaningful
model. The model is useless, unless its purpose is depicted properly.
Hence, learning notations should be emphasized from the very beginning. Different
notations are available for things and relationships. UML diagrams are made using the
notations of things and relationships. Extensibility is another important feature which
makes UML more powerful and flexible.
 The chapter describes basic UML notations in detail. This is just an extension to
the UML building block section discussed in Chapter Two.
Structural Things
Graphical notations used in structural things are most widely used in UML. These are
considered as the nouns of UML models. Following are the list of structural things.
• Classes
• Object
• Interface
• Collaboration
• Use case
• Active classes
• Components
• Nodes

Class Notation
UML class is represented by the following figure. The diagram is divided into four parts.
• The top section is used to name the class.
• The second one is used to show the attributes of the class.
• The third section is used to describe the operations performed by the class.
• The fourth section is optional to show any additional components.

Classes are used to represent objects. Objects can be anything having properties and
responsibility.

Object Notation
The object is represented in the same way as the class. The only difference is
the name which is underlined as shown in the following figure.
As the object is an actual implementation of a class, which is known as the instance of
a class. Hence, it has the same usage as the class.

Interface Notation
Interface is represented by a circle as shown in the following figure. It has a name
which is generally written below the circle.

Interface is used to describe the functionality without implementation. Interface is just

like a template where you define different functions, not the implementation. When a
class implements the interface, it also implements the functionality as per requirement.
Collaboration Notation
Collaboration is represented by a dotted eclipse as shown in the following figure. It has
a name written inside the eclipse.

Collaboration represents responsibilities. Generally, responsibilities are in a group.

Use Case Notation

Use case is represented as an eclipse with a name inside it. It may contain additional
responsibilities.

Use case is used to capture high level functionalities of a system.

Actor Notation
An actor can be defined as some internal or external entity that interacts with the
system.

An actor is used in a use case diagram to describe the internal or external entities.

Initial State Notation

Initial state is defined to show the start of a process. This notation is used in almost all
diagrams.

The usage of Initial State Notation is to show the starting point of a process.
Final State Notation
Final state is used to show the end of a process. This notation is also used in almost all
diagrams to describe the end.

The usage of Final State Notation is to show the termination point of a process.

Active Class Notation

Active class looks similar to a class with a solid border. Active class is generally used to
describe the concurrent behavior of a system.

Active class is used to represent the concurrency in a system.

Component Notation
A component in UML is shown in the following figure with a name inside. Additional
elements can be added wherever required.

Component is used to represent any part of a system for which UML diagrams are
made.

Node Notation
A node in UML is represented by a square box as shown in the following figure with a
name. A node represents the physical component of the system.
Node is used to represent the physical part of a system such as the server, network,
etc.
Behavioral Things
Dynamic parts are one of the most important elements in UML. UML has a set of
powerful features to represent the dynamic part of software and non-software systems.
These features include interactions and state machines.
Interactions can be of two types −
• Sequential (Represented by sequence diagram)
• Collaborative (Represented by collaboration diagram)

Interaction Notation
Interaction is basically a message exchange between two UML components. The
following diagram represents different notations used in an interaction.

Interaction is used to represent the communication among the components of a system.

State Machine Notation

State machine describes the different states of a component in its life cycle. The
notations are described in the following diagram.
State machine is used to describe different states of a system component. The state
can be active, idle, or any other depending upon the situation.
Grouping Things
Organizing the UML models is one of the most important aspects of the design. In UML,
there is only one element available for grouping and that is package.

Package Notation
Package notation is shown in the following figure and is used to wrap the components
of a system.

Annotational Things
In any diagram, explanation of different elements and their functionalities are very
important. Hence, UML has notes notation to support this requirement.

Note Notation
This notation is shown in the following figure. These notations are used to provide
necessary information of a system.
Relationships
A model is not complete unless the relationships between elements are described
properly. The Relationship gives a proper meaning to a UML model. Following are the
different types of relationships available in UML.
• Dependency
• Association
• Generalization
• Extensibility

Dependency Notation
Dependency is an important aspect in UML elements. It describes the dependent
elements and the direction of dependency.
Dependency is represented by a dotted arrow as shown in the following figure. The
arrow head represents the independent element and the other end represents the
dependent element.

Dependency is used to represent the dependency between two elements of a system

Association Notation
Association describes how the elements in a UML diagram are associated. In simple
words, it describes how many elements are taking part in an interaction.
Association is represented by a dotted line with (without) arrows on both sides. The two
ends represent two associated elements as shown in the following figure. The
multiplicity is also mentioned at the ends (1, *, etc.) to show how many objects are
associated.

Association is used to represent the relationship between two elements of a system.

Generalization Notation
Generalization describes the inheritance relationship of the object-oriented world. It is a
parent and child relationship.
Generalization is represented by an arrow with a hollow arrow head as shown in
the following figure. One end represents the parent element and the other end
represents the child element.

Generalization is used to describe parent-child relationship of two elements of a

system.

Extensibility Notation
All the languages (programming or modeling) have some mechanism to extend its
capabilities such as syntax, semantics, etc. UML also has the following mechanisms to
provide extensibility features.
• Stereotypes (Represents new elements)
• Tagged values (Represents new attributes)
• Constraints (Represents the boundaries)

Extensibility notations are used to enhance the power of the language. It is basically
additional elements used to represent some extra behavior of the system. These extra
behaviors are not covered by the standard available notations.
UML - Standard Diagrams
The elements are like components which can be associated in different ways to
make a complete UML picture, which is known as diagram. Thus, it is very important to
understand the different diagrams to implement the knowledge in real-life systems.
Any complex system is best understood by making some kind of diagrams or pictures.
These diagrams have a better impact on our understanding. If we look around, we will
realize that the diagrams are not a new concept but it is used widely in different forms in
different industries.
We prepare UML diagrams to understand the system in a better and simple way.
A single diagram is not enough to cover all the aspects of the system. UML defines
various kinds of diagrams to cover most of the aspects of a system.
You can also create your own set of diagrams to meet your requirements. Diagrams are
generally made in an incremental and iterative way.
There are two broad categories of diagrams and they are again divided into
subcategories −
• Structural Diagrams
• Behavioral Diagrams

Structural Diagrams
The structural diagrams represent the static aspect of the system. These static
aspects represent those parts of a diagram, which forms the main structure and are
therefore stable.
These static parts are represented by classes, interfaces, objects, components, and
nodes. The four structural diagrams are −
• Class diagram
• Object diagram
• Component diagram
• Deployment diagram
Class Diagram
Class diagrams are the most common diagrams used in UML. Class diagram consists
of classes, interfaces, associations, and collaboration. Class diagrams basically
represent the object-oriented view of a system, which is static in nature.
Active class is used in a class diagram to represent the concurrency of the
system.
Class diagram represents the object orientation of a system. Hence, it is generally used
for development purpose. This is the most widely used diagram at the time of system
construction.
Object Diagram
Object diagrams can be described as an instance of class diagram. Thus, these
diagrams are more close to real-life scenarios where we implement a system.
Object diagrams are a set of objects and their relationship is just like class
diagrams. They also represent the static view of the system.
The usage of object diagrams is similar to class diagrams but they are used to
build prototype of a system from a practical perspective.
Component Diagram
Component diagrams represent a set of components and their relationships. These
components consist of classes, interfaces, or collaborations. Component diagrams
represent the implementation view of a system.
During the design phase, software artifacts (classes, interfaces, etc.) of a system
are arranged in different groups depending upon their relationship. Now, these groups
are known as components.
Finally, it can be said component diagrams are used to visualize the
implementation.
Deployment Diagram
Deployment diagrams are a set of nodes and their relationships. These nodes
are physical entities where the components are deployed.
Deployment diagrams are used for visualizing the deployment view of a system.
This is generally used by the deployment team.
Note − If the above descriptions and usages are observed carefully then it is very clear
that all the diagrams have some relationship with one another. Component diagrams
are dependent upon the classes, interfaces, etc. which are part of class/object diagram.
Again, the deployment diagram is dependent upon the components, which are used to
make component diagrams.

Behavioral Diagrams
Any system can have two aspects, static and dynamic. So, a model is considered
as complete when both the aspects are fully covered.
Behavioral diagrams basically capture the dynamic aspect of a system. Dynamic
aspect can be further described as the changing/moving parts of a system.
UML has the following five types of behavioral diagrams −
• Use case diagram
• Sequence diagram
• Collaboration diagram
• Statechart diagram
• Activity diagram

Use Case Diagram

Use case diagrams are a set of use cases, actors, and their relationships. They
represent the use case view of a system.
A use case represents a particular functionality of a system. Hence, use case
diagram is used to describe the relationships among the functionalities and their
internal/external controllers. These controllers are known as actors.
Sequence Diagram
A sequence diagram is an interaction diagram. From the name, it is clear that the
diagram deals with some sequences, which are the sequence of messages flowing
from one object to another.
Interaction among the components of a system is very important from
implementation and execution perspective. Sequence diagram is used to visualize the
sequence of calls in a system to perform a specific functionality.
Collaboration Diagram
Collaboration diagram is another form of interaction diagram. It represents the
structural organization of a system and the messages sent/received. Structural
organization consists of objects and links.
The purpose of collaboration diagram is similar to sequence diagram. However,
the specific purpose of collaboration diagram is to visualize the organization of objects
and their interaction.
Statechart Diagram
Any real-time system is expected to be reacted by some kind of internal/external
events. These events are responsible for state change of the system.
Statechart diagram is used to represent the event driven state change of a
system. It basically describes the state change of a class, interface, etc.
State chart diagram is used to visualize the reaction of a system by
internal/external factors.
Activity Diagram
Activity diagram describes the flow of control in a system. It consists of activities
and links. The flow can be sequential, concurrent, or branched.
Activities are nothing but the functions of a system. Numbers of activity diagrams
are prepared to capture the entire flow in a system.
Activity diagrams are used to visualize the flow of controls in a system. This is
prepared to have an idea of how the system will work when executed.
Note − Dynamic nature of a system is very difficult to capture. UML has provided
features to capture the dynamics of a system from different angles. Sequence diagrams
and collaboration diagrams are isomorphic, hence they can be converted from one
another without losing any information. This is also true for Statechart and activity
diagram.

UML - Class Diagram

Class diagram is a static diagram. It represents the static view of an application. Class
diagram is not only used for visualizing, describing, and documenting different aspects
of a system but also for constructing executable code of the software application.
Class diagram describes the attributes and operations of a class and also the
constraints imposed on the system. The class diagrams are widely used in the
modeling of objectoriented systems because they are the only UML diagrams, which
can be mapped directly with object-oriented languages.
Class diagram shows a collection of classes, interfaces, associations,
collaborations, and constraints. It is also known as a structural diagram.

Purpose of Class Diagrams

The purpose of class diagram is to model the static view of an application. Class
diagrams are the only diagrams which can be directly mapped with object-oriented
languages and thus widely used at the time of construction.
UML diagrams like activity diagram, sequence diagram can only give the
sequence flow of the application, however class diagram is a bit different. It is the most
popular UML diagram in the coder community.
The purpose of the class diagram can be summarized as −
• Analysis and design of the static view of an application.
• Describe responsibilities of a system.
• Base for component and deployment diagrams.
• Forward and reverse engineering.

How to Draw a Class Diagram?

Class diagrams are the most popular UML diagrams used for construction of software
applications. It is very important to learn the drawing procedure of class diagram.
Class diagrams have a lot of properties to consider while drawing but here the diagram
will be considered from a top level view.
Class diagram is basically a graphical representation of the static view of the system
and represents different aspects of the application. A collection of class diagrams
represent the whole system.
The following points should be remembered while drawing a class diagram −
• The name of the class diagram should be meaningful to describe the aspect of
the system.
• Each element and their relationships should be identified in advance.
 • Responsibility (attributes and methods) of each class should be clearly identified
• For each class, minimum number of properties should be specified, as
unnecessary properties will make the diagram complicated.
• Use notes whenever required to describe some aspect of the diagram. At the end
of the drawing it should be understandable to the developer/coder.
• Finally, before making the final version, the diagram should be drawn on plain
paper and reworked as many times as possible to make it correct.
The following diagram is an example of an Order System of an application. It describes
a particular aspect of the entire application.
• First of all, Order and Customer are identified as the two elements of the system.
They have a one-to-many relationship because a customer can have multiple
orders.
• Order class is an abstract class and it has two concrete classes (inheritance
relationship) SpecialOrder and NormalOrder.
• The two inherited classes have all the properties as the Order class. In addition,
they have additional functions like dispatch () and receive ().
The following class diagram has been drawn considering all the points mentioned
above.
Where to Use Class Diagrams?
Class diagram is a static diagram and it is used to model the static view of a system.
The static view describes the vocabulary of the system.
Class diagram is also considered as the foundation for component and deployment
diagrams. Class diagrams are not only used to visualize the static view of the system
but they are also used to construct the executable code for forward and reverse
engineering of any system.
Generally, UML diagrams are not directly mapped with any object-oriented
programming languages but the class diagram is an exception.
Class diagram clearly shows the mapping with object-oriented languages such as Java,
C++, etc. From practical experience, class diagram is generally used for construction
purpose.
In a nutshell it can be said, class diagrams are used for −
• Describing the static view of the system.
• Showing the collaboration among the elements of the static view.
• Describing the functionalities performed by the system.
• Construction of software applications using object oriented languages.

UML - Object Diagrams

Object diagrams are derived from class diagrams so object diagrams are dependent
upon class diagrams.
Object diagrams represent an instance of a class diagram. The basic concepts are
similar for class diagrams and object diagrams. Object diagrams also represent the
static view of a system but this static view is a snapshot of the system at a particular
moment.
Object diagrams are used to render a set of objects and their relationships as an
instance.
Purpose of Object Diagrams
The purpose of a diagram should be understood clearly to implement it practically. The
purposes of object diagrams are similar to class diagrams.
The difference is that a class diagram represents an abstract model consisting of
classes and their relationships. However, an object diagram represents an instance at a
particular moment, which is concrete in nature.
It means the object diagram is closer to the actual system behavior. The purpose is to
capture the static view of a system at a particular moment.
The purpose of the object diagram can be summarized as −
• Forward and reverse engineering.
• Object relationships of a system
• Static view of an interaction.
• Understand object behaviour and their relationship from practical perspective

How to Draw an Object Diagram?

We have already discussed that an object diagram is an instance of a class diagram. It
implies that an object diagram consists of instances of things used in a class diagram.
So both diagrams are made of same basic elements but in different form. In class
diagram elements are in abstract form to represent the blue print and in object diagram
the elements are in concrete form to represent the real world object.
To capture a particular system, numbers of class diagrams are limited. However, if we
consider object diagrams then we can have unlimited number of instances, which are
unique in nature. Only those instances are considered, which have an impact on the
system.
From the above discussion, it is clear that a single object diagram cannot capture all the
necessary instances or rather cannot specify all the objects of a system. Hence, the
solution is −
• First, analyze the system and decide which instances have important data and
association.
• Second, consider only those instances, which will cover the functionality.
• Third, make some optimization as the number of instances are unlimited.
Before drawing an object diagram, the following things should be remembered and
understood clearly −
• Object diagrams consist of objects.
• The link in object diagram is used to connect objects.
• Objects and links are the two elements used to construct an object diagram.
After this, the following things are to be decided before starting the construction of the
diagram −
• The object diagram should have a meaningful name to indicate its purpose.
• The most important elements are to be identified.
• The association among objects should be clarified.
• Values of different elements need to be captured to include in the object diagram.
• Add proper notes at points where more clarity is required.
The following diagram is an example of an object diagram. It represents the Order
management system which we have discussed in the chapter Class Diagram. The
following diagram is an instance of the system at a particular time of purchase. It has
the following objects.
• Customer
• Order
• SpecialOrder
• NormalOrder
Now the customer object (C) is associated with three order objects (O1, O2, and O3).
These order objects are associated with special order and normal order objects (S1,
S2, and N1). The customer has the following three orders with different numbers (12,
32 and 40) for the particular time considered.
The customer can increase the number of orders in future and in that scenario
the object diagram will reflect that. If order, special order, and normal order objects are
observed then you will find that they have some values.
For orders, the values are 12, 32, and 40 which implies that the objects have
these values for a particular moment (here the particular time when the purchase is
made is considered as the moment) when the instance is captured
The same is true for special order and normal order objects which have number of
orders as 20, 30, and 60. If a different time of purchase is considered, then these
values will change accordingly.
The following object diagram has been drawn considering all the points mentioned
above

Where to Use Object Diagrams?

Object diagrams can be imagined as the snapshot of a running system at a particular
moment. Let us consider an example of a running train
Now, if you take a snap of the running train then you will find a static picture of it having
the following −
• A particular state which is running.
• A particular number of passengers. which will change if the snap is taken in a
different time
Here, we can imagine the snap of the running train is an object having the above
values. And this is true for any real-life simple or complex system.
In a nutshell, it can be said that object diagrams are used for −
• Making the prototype of a system.
• Reverse engineering.
• Modeling complex data structures.
• Understanding the system from practical perspective.
UML - Component Diagrams
Component diagrams are different in terms of nature and behavior. Component
diagrams are used to model the physical aspects of a system. Now the question is,
what are these physical aspects? Physical aspects are the elements such as
executables, libraries, files, documents, etc. which reside in a node.
Component diagrams are used to visualize the organization and relationships among
components in a system. These diagrams are also used to make executable systems.

Purpose of Component Diagrams

Component diagram is a special kind of diagram in UML. The purpose is also different
from all other diagrams discussed so far. It does not describe the functionality of the
system but it describes the components used to make those functionalities.
Thus from that point of view, component diagrams are used to visualize the physical
components in a system. These components are libraries, packages, files, etc.
Component diagrams can also be described as a static implementation view of a
system. Static implementation represents the organization of the components at a
particular moment.
A single component diagram cannot represent the entire system but a collection of
diagrams is used to represent the whole.
The purpose of the component diagram can be summarized as −
• Visualize the components of a system.
• Construct executables by using forward and reverse engineering.
• Describe the organization and relationships of the components.

How to Draw a Component Diagram?

Component diagrams are used to describe the physical artifacts of a system. This
artifact includes files, executables, libraries, etc
The purpose of this diagram is different. Component diagrams are used during the
implementation phase of an application. However, it is prepared well in advance to
visualize the implementation details.
Initially, the system is designed using different UML diagrams and then when the
artifacts are ready, component diagrams are used to get an idea of the implementation.
This diagram is very important as without it the application cannot be implemented
efficiently. A well-prepared component diagram is also important for other aspects such
as application performance, maintenance, etc.
Before drawing a component diagram, the following artifacts are to be identified clearly
• Files used in the system.
• Libraries and other artifacts relevant to the application.
• Relationships among the artifacts.
After identifying the artifacts, the following points need to be kept in mind.
• Use a meaningful name to identify the component for which the diagram is to be
drawn.
• Prepare a mental layout before producing the using tools.
• Use notes for clarifying important points.
Following is a component diagram for order management system. Here, the artifacts
are files. The diagram shows the files in the application and their relationships. In
actual, the component diagram also contains dlls, libraries, folders, etc.
In the following diagram, four files are identified and their relationships are produced.
Component diagram cannot be matched directly with other UML diagrams discussed so
far as it is drawn for completely different purpose.
The following component diagram has been drawn considering all the points mentioned
above.
Where to Use Component Diagrams?
We have already described that component diagrams are used to visualize the static
implementation view of a system. Component diagrams are special type of UML
diagrams used for different purposes.
These diagrams show the physical components of a system. To clarify it, we can say
that component diagrams describe the organization of the components in a system.
Organization can be further described as the location of the components in a system.
These components are organized in a special way to meet the system requirements.
As we have already discussed, those components are libraries, files, executables, etc.
Before implementing the application, these components are to be organized. This
component organization is also designed separately as a part of project execution.
Component diagrams are very important from implementation perspective. Thus, the
implementation team of an application should have a proper knowledge of the
component details
Component diagrams can be used to −
• Model the components of a system.
• Model the database schema.
• Model the executables of an application.
• Model the system's source code.
UML - Deployment Diagrams
Deployment diagrams are used to visualize the topology of the physical components of
a system, where the software components are deployed.
Deployment diagrams are used to describe the static deployment view of a system.
Deployment diagrams consist of nodes and their relationships.

Purpose of Deployment Diagrams

The term Deployment itself describes the purpose of the diagram. Deployment
diagrams are used for describing the hardware components, where software
components are deployed. Component diagrams and deployment diagrams are closely
related.
Component diagrams are used to describe the components and deployment diagrams
shows how they are deployed in hardware.
UML is mainly designed to focus on the software artifacts of a system. However, these
two diagrams are special diagrams used to focus on software and hardware
components.
Most of the UML diagrams are used to handle logical components but deployment
diagrams are made to focus on the hardware topology of a system. Deployment
diagrams are used by the system engineers.
The purpose of deployment diagrams can be described as −
• Visualize the hardware topology of a system.
• Describe the hardware components used to deploy software components.
• Describe the runtime processing nodes.

How to Draw a Deployment Diagram?

Deployment diagram represents the deployment view of a system. It is related to the
component diagram because the components are deployed using the deployment
diagrams. A deployment diagram consists of nodes. Nodes are nothing but physical
hardware used to deploy the application.
Deployment diagrams are useful for system engineers. An efficient deployment diagram
is very important as it controls the following parameters −
 • Performance
• Scalability
• Maintainability
• Portability
Before drawing a deployment diagram, the following artifacts should be identified −
• Nodes
• Relationships among nodes
Following is a sample deployment diagram to provide an idea of the deployment view of
order management system. Here, we have shown nodes as −
• Monitor
• Modem
• Caching server
• Server
The application is assumed to be a web-based application, which is deployed in a
clustered environment using server 1, server 2, and server 3. The user connects to the
application using the Internet. The control flows from the caching server to the clustered
environment.
The following deployment diagram has been drawn considering all the points
mentioned above.
Where to Use Deployment Diagrams?
Deployment diagrams are mainly used by system engineers. These diagrams are used
to describe the physical components (hardware), their distribution, and association.
Deployment diagrams can be visualized as the hardware components/nodes on which
the software components reside.
Software applications are developed to model complex business processes. Efficient
software applications are not sufficient to meet the business requirements. Business
requirements can be described as the need to support the increasing number of users,
quick response time, etc.
To meet these types of requirements, hardware components should be designed
efficiently and in a cost-effective way.
Now-a-days software applications are very complex in nature. Software applications
can be standalone, web-based, distributed, mainframe-based and many more. Hence,
it is very important to design the hardware components efficiently.
Deployment diagrams can be used −
• To model the hardware topology of a system.
• To model the embedded system.
• To model the hardware details for a client/server system.
• To model the hardware details of a distributed application.
• For Forward and Reverse engineering.

UML - Use Case Diagrams

o model a system, the most important aspect is to capture the dynamic behavior.
Dynamic behavior means the behavior of the system when it is running/operating.
Only static behavior is not sufficient to model a system rather dynamic behavior is more
important than static behavior. In UML, there are five diagrams available to model the
dynamic nature and use case diagram is one of them. Now as we have to discuss that
the use case diagram is dynamic in nature, there should be some internal or external
factors for making the interaction.
These internal and external agents are known as actors. Use case diagrams consists of
actors, use cases and their relationships. The diagram is used to model the
system/subsystem of an application. A single use case diagram captures a particular
functionality of a system.
Hence to model the entire system, a number of use case diagrams are used.

Purpose of Use Case Diagrams

The purpose of use case diagram is to capture the dynamic aspect of a system.
However, this definition is too generic to describe the purpose, as other four diagrams
(activity, sequence, collaboration, and Statechart) also have the same purpose. We will
look into some specific purpose, which will distinguish it from other four diagrams.
Use case diagrams are used to gather the requirements of a system including internal
and external influences. These requirements are mostly design requirements. Hence,
when a system is analyzed to gather its functionalities, use cases are prepared and
actors are identified.
When the initial task is complete, use case diagrams are modelled to present the
outside view.
In brief, the purposes of use case diagrams can be said to be as follows −
• Used to gather the requirements of a system.
• Used to get an outside view of a system.
• Identify the external and internal factors influencing the system.
• Show the interaction among the requirements are actors.

How to Draw a Use Case Diagram?

Use case diagrams are considered for high level requirement analysis of a system.
When the requirements of a system are analyzed, the functionalities are captured in
use cases.
We can say that use cases are nothing but the system functionalities written in an
organized manner. The second thing which is relevant to use cases are the actors.
Actors can be defined as something that interacts with the system.
Actors can be a human user, some internal applications, or may be some external
applications. When we are planning to draw a use case diagram, we should have the
following items identified.
• Functionalities to be represented as use case
 • Actors
• Relationships among the use cases and actors.
Use case diagrams are drawn to capture the functional requirements of a system. After
identifying the above items, we have to use the following guidelines to draw an efficient
use case diagram
• The name of a use case is very important. The name should be chosen in such a
way so that it can identify the functionalities performed.
• Give a suitable name for actors.
• Show relationships and dependencies clearly in the diagram.
• Do not try to include all types of relationships, as the main purpose of the
diagram is to identify the requirements.
• Use notes whenever required to clarify some important points.
Following is a sample use case diagram representing the order management system.
Hence, if we look into the diagram then we will find three use cases (Order,
SpecialOrder, and NormalOrder) and one actor which is the customer.
The SpecialOrder and NormalOrder use cases are extended from Order use case.
Hence, they have extended relationship. Another important point is to identify the
system boundary, which is shown in the picture. The actor Customer lies outside the
system as it is an external user of the system.

Where to Use a Use Case Diagram?

As we have already discussed there are five diagrams in UML to model the
dynamic view of a system. Now each and every model has some specific purpose to
use. Actually these specific purposes are different angles of a running system.
 To understand the dynamics of a system, we need to use different types of
diagrams. Use case diagram is one of them and its specific purpose is to gather system
requirements and actors.
Use case diagrams specify the events of a system and their flows. But use case
diagram never describes how they are implemented. Use case diagram can be
imagined as a black box where only the input, output, and the function of the black box
is known.
These diagrams are used at a very high level of design. This high level design is
refined again and again to get a complete and practical picture of the system. A well-
structured use case also describes the pre-condition, post condition, and exceptions.
These extra elements are used to make test cases when performing the testing.
Although use case is not a good candidate for forward and reverse engineering, still
they are used in a slightly different way to make forward and reverse engineering. The
same is true for reverse engineering. Use case diagram is used differently to make it
suitable for reverse engineering.
In forward engineering, use case diagrams are used to make test cases and in
reverse engineering use cases are used to prepare the requirement details from the
existing application.
Use case diagrams can be used for −
• Requirement analysis and high level design.
• Model the context of a system.
• Reverse engineering.
• Forward engineering.

UML - Interaction Diagrams

From the term Interaction, it is clear that the diagram is used to describe some type of
interactions among the different elements in the model. This interaction is a part of
dynamic behavior of the system.
This interactive behavior is represented in UML by two diagrams known
as Sequence diagram and Collaboration diagram. The basic purpose of both the
diagrams are similar.
Sequence diagram emphasizes on time sequence of messages and collaboration
diagram emphasizes on the structural organization of the objects that send and receive
messages.

Purpose of Interaction Diagrams

The purpose of interaction diagrams is to visualize the interactive behavior of the
system. Visualizing the interaction is a difficult task. Hence, the solution is to use
different types of models to capture the different aspects of the interaction.
Sequence and collaboration diagrams are used to capture the dynamic nature but from
a different angle.
The purpose of interaction diagram is −
• To capture the dynamic behaviour of a system.
• To describe the message flow in the system.
• To describe the structural organization of the objects.
• To describe the interaction among objects.

How to Draw an Interaction Diagram?

As we have already discussed, the purpose of interaction diagrams is to capture
the dynamic aspect of a system. So to capture the dynamic aspect, we need to
understand what a dynamic aspect is and how it is visualized. Dynamic aspect can be
defined as the snapshot of the running system at a particular moment
We have two types of interaction diagrams in UML. One is the sequence diagram
and the other is the collaboration diagram. The sequence diagram captures the time
sequence of the message flow from one object to another and the collaboration
diagram describes the organization of objects in a system taking part in the message
flow.
Following things are to be identified clearly before drawing the interaction diagram
• Objects taking part in the interaction.
• Message flows among the objects.
• The sequence in which the messages are flowing.
• Object organization.
Following are two interaction diagrams modeling the order management system. The
first diagram is a sequence diagram and the second is a collaboration diagram
The Sequence Diagram
The sequence diagram has four objects (Customer, Order, SpecialOrder and
NormalOrder).
The following diagram shows the message sequence for SpecialOrder object and
the same can be used in case of NormalOrder object. It is important to understand the
time sequence of message flows. The message flow is nothing but a method call of an
object.
The first call is sendOrder () which is a method of Order object. The next call is confirm
() which is a method of SpecialOrder object and the last call is Dispatch () which is a
method of SpecialOrder object. The following diagram mainly describes the method
calls from one object to another, and this is also the actual scenario when the system is
running.

The Collaboration Diagram

The second interaction diagram is the collaboration diagram. It shows the object
organization as seen in the following diagram. In the collaboration diagram, the method
call sequence is indicated by some numbering technique. The number indicates how
the methods are called one after another. We have taken the same order management
system to describe the collaboration diagram.
 Method calls are similar to that of a sequence diagram. However, difference
being the sequence diagram does not describe the object organization, whereas the
collaboration diagram shows the object organization.
To choose between these two diagrams, emphasis is placed on the type of
requirement. If the time sequence is important, then the sequence diagram is used. If
organization is required, then collaboration diagram is used.

Where to Use Interaction Diagrams?

We have already discussed that interaction diagrams are used to describe the
dynamic nature of a system. Now, we will look into the practical scenarios where these
diagrams are used. To understand the practical application, we need to understand the
basic nature of sequence and collaboration diagram.
The main purpose of both the diagrams are similar as they are used to capture
the dynamic behavior of a system. However, the specific purpose is more important to
clarify and understand.
Sequence diagrams are used to capture the order of messages flowing from one
object to another. Collaboration diagrams are used to describe the structural
organization of the objects taking part in the interaction. A single diagram is not
sufficient to describe the dynamic aspect of an entire system, so a set of diagrams are
used to capture it as a whole.
Interaction diagrams are used when we want to understand the message flow
and the structural organization. Message flow means the sequence of control flow from
one object to another. Structural organization means the visual organization of the
elements in a system.
Interaction diagrams can be used −
• To model the flow of control by time sequence.
• To model the flow of control by structural organizations.
• For forward engineering.
• For reverse engineering.

UML - Statechart Diagrams

The name of the diagram itself clarifies the purpose of the diagram and other details. It
describes different states of a component in a system. The states are specific to a
component/object of a system.
A Statechart diagram describes a state machine. State machine can be defined as a
machine which defines different states of an object and these states are controlled by
external or internal events.
Activity diagram explained in the next chapter, is a special kind of a Statechart diagram.
As Statechart diagram defines the states, it is used to model the lifetime of an object.

Purpose of Statechart Diagrams

Statechart diagram is one of the five UML diagrams used to model the dynamic nature
of a system. They define different states of an object during its lifetime and these states
are changed by events. Statechart diagrams are useful to model the reactive systems.
Reactive systems can be defined as a system that responds to external or internal
events.
Statechart diagram describes the flow of control from one state to another state. States
are defined as a condition in which an object exists and it changes when some event is
triggered. The most important purpose of Statechart diagram is to model lifetime of an
object from creation to termination.
Statechart diagrams are also used for forward and reverse engineering of a system.
However, the main purpose is to model the reactive system.
Following are the main purposes of using Statechart diagrams −
• To model the dynamic aspect of a system.
• To model the life time of a reactive system.
• To describe different states of an object during its life time.
 • Define a state machine to model the states of an object.

How to Draw a Statechart Diagram?

Statechart diagram is used to describe the states of different objects in its life cycle.
Emphasis is placed on the state changes upon some internal or external events. These
states of objects are important to analyze and implement them accurately.
Statechart diagrams are very important for describing the states. States can be
identified as the condition of objects when a particular event occurs.
Before drawing a Statechart diagram we should clarify the following points −
• Identify the important objects to be analyzed.
• Identify the states.
• Identify the events.
Following is an example of a Statechart diagram where the state of Order object is
analyzed
The first state is an idle state from where the process starts. The next states are arrived
for events like send request, confirm request, and dispatch order. These events are
responsible for the state changes of order object.
During the life cycle of an object (here order object) it goes through the following states
and there may be some abnormal exits. This abnormal exit may occur due to some
problem in the system. When the entire life cycle is complete, it is considered as a
complete transaction as shown in the following figure. The initial and final state of an
object is also shown in the following figure.
Where to Use Statechart Diagrams?
From the above discussion, we can define the practical applications of a
Statechart diagram. Statechart diagrams are used to model the dynamic aspect of a
system like other four diagrams discussed in this tutorial. However, it has some
distinguishing characteristics for modeling the dynamic nature.
Statechart diagram defines the states of a component and these state changes
are dynamic in nature. Its specific purpose is to define the state changes triggered by
events. Events are internal or external factors influencing the system.
Statechart diagrams are used to model the states and also the events operating
on the system. When implementing a system, it is very important to clarify different
states of an object during its life time and Statechart diagrams are used for this
purpose. When these states and events are identified, they are used to model it and
these models are used during the implementation of the system.
If we look into the practical implementation of Statechart diagram, then it is
mainly used to analyze the object states influenced by events. This analysis is helpful to
understand the system behavior during its execution.
The main usage can be described as −
• To model the object states of a system.
• To model the reactive system. Reactive system consists of reactive objects.
• To identify the events responsible for state changes.
• Forward and reverse engineering.

UML - Activity Diagrams

Activity diagram is another important diagram in UML to describe the dynamic aspects
of the system.
Activity diagram is basically a flowchart to represent the flow from one activity to
another activity. The activity can be described as an operation of the system.
The control flow is drawn from one operation to another. This flow can be sequential,
branched, or concurrent. Activity diagrams deal with all type of flow control by using
different elements such as fork, join, etc
Purpose of Activity Diagrams
The basic purposes of activity diagrams is similar to other four diagrams. It
captures the dynamic behavior of the system. Other four diagrams are used to show
the message flow from one object to another but activity diagram is used to show
message flow from one activity to another.
Activity is a particular operation of the system. Activity diagrams are not only
used for visualizing the dynamic nature of a system, but they are also used to construct
the executable system by using forward and reverse engineering techniques. The only
missing thing in the activity diagram is the message part.
It does not show any message flow from one activity to another. Activity diagram
is sometimes considered as the flowchart. Although the diagrams look like a flowchart,
they are not. It shows different flows such as parallel, branched, concurrent, and single.
The purpose of an activity diagram can be described as −
• Draw the activity flow of a system.
• Describe the sequence from one activity to another.
• Describe the parallel, branched and concurrent flow of the system.

How to Draw an Activity Diagram?

Activity diagrams are mainly used as a flowchart that consists of activities
performed by the system. Activity diagrams are not exactly flowcharts as they have
some additional capabilities. These additional capabilities include branching, parallel
flow, swimlane, etc.
Before drawing an activity diagram, we must have a clear understanding about
the elements used in activity diagram. The main element of an activity diagram is the
activity itself. An activity is a function performed by the system. After identifying the
activities, we need to understand how they are associated with constraints and
conditions.
Before drawing an activity diagram, we should identify the following elements −
• Activities
• Association
• Conditions
 • Constraints
Once the above-mentioned parameters are identified, we need to make a mental layout
of the entire flow. This mental layout is then transformed into an activity diagram.
Following is an example of an activity diagram for order management system. In the
diagram, four activities are identified which are associated with conditions. One
important point should be clearly understood that an activity diagram cannot be exactly
matched with the code. The activity diagram is made to understand the flow of activities
and is mainly used by the business users
Following diagram is drawn with the four main activities −
• Send order by the customer
• Receipt of the order
• Confirm the order
• Dispatch the order
After receiving the order request, condition checks are performed to check if it is normal
or special order. After the type of order is identified, dispatch activity is performed and
that is marked as the termination of the process.

Where to Use Activity Diagrams?

The basic usage of activity diagram is similar to other four UML diagrams. The
specific usage is to model the control flow from one activity to another. This control flow
does not include messages.
Activity diagram is suitable for modeling the activity flow of the system. An
application can have multiple systems. Activity diagram also captures these systems
and describes the flow from one system to another. This specific usage is not available
in other diagrams. These systems can be database, external queues, or any other
system.
We will now look into the practical applications of the activity diagram. From the
above discussion, it is clear that an activity diagram is drawn from a very high level. So
it gives high level view of a system. This high level view is mainly for business users or
any other person who is not a technical person.
This diagram is used to model the activities which are nothing but business
requirements. The diagram has more impact on business understanding rather than on
implementation details.
Activity diagram can be used for −
• Modeling work flow by using activities.
• Modeling business requirements.
• High level understanding of the system's functionalities.
• Investigating business requirements at a later stage.