Wireless web-Web
services
The wireless web represents the combination of two innovative
technologies— wireless communications and the Internet.
A generic term for untethered access to the Web and other Inter
net services such as email and chat.
Public and private hotspots, Internet access via cellphone and
all other fixed or mobile wireless access services make up the
wireless Web.
Example: Amazon Web Services , Google’s Web service,
Google Cloud Platform.
Wireless web-Web services
On the World Wide Web, a web service is a standardized method for
propagating messages between client and server applications.
A web service is a set of open protocols and standards that allow data
to be exchanged between different applications or systems. Web
services can be used by software programs written in a variety of
programming languages and running on a variety of platforms to
exchange data via computer networks such as the Internet in a similar
way to inter-process communication on a single computer.
Web services are XML-centered data exchange systems that use the
internet for A2A (application-to-application) communication and
interfacing. These processes involve programs, messages, documents,
and/or objects.
A key feature of web services is that applications can be written in
various languages and are still able to communicate by exchanging
data with one another via a web service between clients and servers. A
client summons a web service by sending a request via XML, and the
service then responses with an XML response. Web services are also
often associated with SOA (Service-Oriented Architecture).
What is mobile web service?
The Mobile Web refers to access to the world wide web, i.e. the
use of browser-based Internet services, from a handheld mobile
device, such as a smartphone, a feature phone or a tablet
computer, connected to a mobile network or other wireless
network.
Mobile web interface- A mobile user interface (mobile UI) is the
graphical and usually touch-sensitive display on a mobile
device, such as a smartphone or tablet, that allows the user to
interact with the device's apps, features, content and functions.
Web apps, are accessed via the internet browser and will adapt
to whichever device you're viewing them on.
Functions of Web Services
It’s possible to access it via the internet or intranet
networks.
XML messaging protocol that is standardized.
Operating system or programming language independent.
Using the XML standard, it is self-describing.
A simple location approach can be used to locate it.
How Does Web Service Work?
The diagram depicts a very simplified version of how a web service
would function. The client would use requests to send a sequence of
web service calls to a server that would host the actual web service.
Remote procedure calls are what are used to make these requests.
Calls to methods hosted by the relevant web service are known as
Remote Procedure Calls (RPC).
Example: Flipkart offers a web service that displays prices for items
offered on Flipkart.com. The front end or presentation layer can be
written in .Net or Java, but the web service can be communicated using
either programming language.
The data that is exchanged between the client and the server, which is
XML, is the most important part of a web service design.
For transmitting XML data between applications, web services employ
SOAP (Simple Object Access Protocol). The data is sent using
standard HTTP. A SOAP message is data that is sent from the web
service to the application.
Components of Web Service
XML and HTTP is the most fundamental web services platform.
The following components are used by all typical web services:
1) SOAP (Simple Object Access Protocol)
2) UDDI (Universal Description, Discovery, and Integration)
3) WSDL (Web Services Description Language)
Components of Web Service
1. SOAP (Simple Object Access Protocol)
SOAP is a standard protocol that was first designed so that
applications built with different languages and on different
platforms could communicate.
It is a transport-independent messaging protocol.
SOAP was developed as an intermediate language so that
applications built on various programming languages could talk
easily to each other and avoid the extreme development effort.
SOAP is built on sending XML data in the form of SOAP
Messages. A document known as an XML document is attached
to each message. Only the structure of the XML document, not
the content, follows a pattern.
The best thing about Web services and SOAP is that everything
is sent through HTTP, the standard web protocol.
SOAP
SOAP message structure
In an XML document, the root element is the first element. The
“envelope” is separated into two halves. The header comes first,
followed by the body. The routing data, or information that
directs the XML document to which client it should be sent to, is
contained in the header. The real message will be in the body.
Standard SOAP API requests and responses appear as an
enveloped message that consists of four elements with specific
functions for each one.
Headers and fault elements are optional
SOAP
SOAP
Envelope is the core and essential element of every message,
which begins and concludes messages with its tags, enveloping
it, hence the name.
Header (optional) determines the specifics, extra requirements
for the message, e.g. authentication.
Body includes the request or response.
Fault (optional) shows all data about any errors that could
emerge throughout the API request and response.
UDDI (Universal Description, Discovery, and Integration)
2. UDDI (Universal Description, Discovery, and Integration)
UDDI is a standard for specifying, publishing and discovering a
service provider’s online services.
It provides a specification that aids in the hosting of data via web
services. UDDI provides a repository where WSDL(web
services description language) files can be hosted so that a
client application can discover a WSDL file to learn about the
various actions that a web service offers. As a result, the client
application will have full access to the UDDI, which serves as a
database for all WSDL files.
UDDI
UDDI is an XML-based standard for describing, publishing, and
finding web services.
is a specification for a distributed registry of web services. The
UDDI registry will hold the required information for the online
service, just like a telephone directory has the name, address,
and phone number of a certain individual. So that a client
application may figure out where it is.
is a platform-independent, open framework.
can communicate via SOAP, CORBA, Java RMI Protocol.
uses Web Service Definition Language(WSDL) to describe
interfaces to web services.
is seen with SOAP and WSDL as one of the three foundation
standards of web services.
is an open industry initiative, enabling businesses to discover
each other and define how they interact over the Internet.
UDDI - Elements
A business or a company can register three types of information into a
UDDI registry. This information is contained in three elements of UDDI.
These three elements are −
1. White Pages,
2. Yellow Pages, and
3. Green Pages.
White Pages
White pages contain −
• Basic information about the company and its business.
• Basic contact information including business name, address, contact
phone number, etc.
• A Unique identifiers for the company tax IDs. This information allows
others to discover your web service based upon your business
identification.
Yellow Pages
Yellow pages contain more details about the company. They
include descriptions of the kind of electronic capabilities the
company can offer to anyone who wants to do business with it.
Yellow pages uses commonly accepted industrial categorization
schemes, industry codes, product codes, business identification
codes and the like to make it easier for companies to search
through the listings and find exactly what they want.
Green Pages
Green pages contains technical information about a web
service. A green page allows someone to bind to a Web service
after it's been found. It includes −
The various interfaces
The URL locations
Discovery information and similar data required to find and run
the Web service.
WSDL (Web Services Description Language)
3. WSDL (Web Services Description Language)
WSDL stands for Web Services Description Language. It is the
standard format for describing a web service. WSDL was
developed jointly by Microsoft and IBM.
The WSDL file is another XML-based file that explains what the
web service does to the client application. The client application
will be able to understand where the web service is located and
how to use it by using the WSDL document.
Features of WSDL
WSDL is an XML-based protocol for information exchange in
decentralized and distributed environments.
WSDL definitions describe how to access a web service and
what operations it will perform.
WSDL is a language for describing how to interface with
XML-based services.
WSDL is an integral part of Universal Description, Discovery,
and Integration (UDDI), an XML-based worldwide business
registry.
WSDL is the language that UDDI uses.
WSDL Usage
WSDL is often used in combination with SOAP and XML
Schema to provide web services over the Internet. A client
program connecting to a web service can read the WSDL to
determine what functions are available on the server. Any
special datatypes used are embedded in the WSDL file in the
form of XML Schema. The client can then use SOAP to actually
call one of the functions listed in the WSDL.
WSDL Document Elements
Definitions: It is the basic element of the WSDL document that
contains the definition of one or more services.
Types: The Type element is used to give information about the
complicated data types used within the WSDL document.
Message: It contains abstract data that is being used in
communication between client and web server. It also defines
the data elements for each operation.
portType: It contains the collection of abstract operation
supported by one or more endpoints.
Port: It is used to define the single endpoint as an address for
the binding.
Services: It is a collection of endpoint networks that specify the
port address for the binding.
Binding: It specifies how operations are implemented by
concrete protocols and data format features for operation and
messaging.
API vs. Web Services
Web services and APIs are often mistaken for each other, which
isn’t all that surprising since there is some distinct common
ground.
Most web services provide an API, which, with its set of
commands and functions, is used to retrieve data. Here’s one
example: Twitter delivers an API that authorizes a developer
access tweets from a server and then collects data in JSON
format.
Differences between APIs and Web Services
APIs can be hosted within an app or IIS (Internet Information
Services), but a web service can only be hosted on IIS.
Web services are not an open source and are used to
understand JSON (JavaScript Object Notation) or XML, whereas
APIs are an open source and only used for XML.
API is a light-weight architecture (best for limited bandwidth
devices (e.g. smartphone). Web services are not lightweight
architectures since they require SOAP to send and receive
network data.
APIs can use any form of communication, but a Web service
only uses SOAP, REST, and XML-RPC.
APIs support URL, request/response headers, caching,
versioning, content formats. Web services only support HTTP.
Similarities between APIs and Web Services
Both are accessed through HTTP/HTTPS to enable
communication between services providers and customers.
Both call a function, process data, and receive a response
Wireless middleware
Wireless middleware
Wireless middleware is an intermediate software component that is generally
located on a wired network between the wireless device and the application or
data residing on a wired network,
The purpose of the middleware is to increase performance of applications
running across the wireless network by serving as a communication facilitator
between components that run on wireless and wired devices (Wireless Nets)
It serves as a communication facilitator by addressing the numerous ways in
which communication can fail among components in a distributed application.
Sources of communication failure, among many others, include a component
going off line voluntarily but unexpectedly, a component unexpectedly
terminating, a component failing to respond to a request in a reasonable
amount of time, and communication being severed in the midst of a request
How it Works
Wireless middleware usually consists of client and server
software. The client portion resides on the mobile computer and
accepts messages from applications on the mobile computer. It
reformats these messages and forwards them across the
wireless network using application-layer protocols optimized for
wireless communications. The messages reach the middleware
server, which typically resides on the destination LAN. The
middleware server functions as a gateway to other servers and
hosts on the LAN, acting as a proxy for the mobile computer.
Middleware performs the following functions, though specific
details will vary depending on the actual middleware.
Isolates the application from connectivity issues such as
intermittent connections and varying throughput.
Minimizes the amount of data sent over the wireless connection.
Reduces the number of back-and-forth messages required to
complete a transaction.
Queues messages when a connection is not available.
Provides a consistent API regardless of the underlying network
TYPES OF WIRELESS NETWORKS
1. Fixed Wireless Networks
Fixed Wireless Networks use wireless transmitters with a relatively
short transmission distance .Networks of this type have many of the
characteristics of fixed wire networks, such as low latency, high
bandwidth, and relatively good reliability.
2. Highly Mobile Wireless Networks
These wireless networks are used predominately to serve highly
mobile clients such as mobile cellular phones or satellite
communications. Networks of this type have extremely high latency,
relatively low bandwidth, and greater unreliability, as any number of
interruptions can occur to disrupt the communication with the client.
Wireless Gateway
Wireless Gateway
A wireless gateway routes packets from a wireless LAN to
another network, wired or wireless WAN.
Can be implemented as a software or a hardware or a
combination of both.
Wireless gateways combine the functions of a wireless access
point, a router, and often provide firewall functions as well.
They provide network address translation (NAT) functionality, so
multiple users can use the internet with a single public IP.
It also acts like a dynamic host configuration protocol (DHCP) to
assign IPs automatically to devices connected to the network.
Wireless Gateway
Types of Wireless Gateway:
The simpler kind must be connected to a DSL modem or cable
modem to connect to the internet via the internet service
provider (ISP).
The more complex kind has a built-in modem to connect to the
internet without needing another device. This converged
device saves desk space and simplifies wiring by replacing two
electronic packages with one. It has a wired connection to the
ISP, at least one jack port for the LAN (usually four jacks), and
an antenna for wireless users.
All wireless gateways have the ability to protect the wireless network using
security encryption methods such as WEP(Wired Equivalent
Privacy was a security algorithm for 802.11 wireless networks), WPA
(Wi-Fi Protected Access ), and WPS (Wi-Fi Protected Setup is
a network security standard to create a secure wireless home network).
Is a wireless gateway the same as a router?
A router is a device that is capable of sending and receiving
data packets between computer networks, also creating an
overlay network. A Gateway, on the other hand, joins
dissimilar systems. Gateway it is defined as a network
entity that allows a network to interface with another
network with different protocols.
The Mobile Application Server (MAS)
The Mobile Application Server (MAS)
An Infrastructure Platform for Mobile Wireless Services
Defining Mobile Computing Application Server
Mobile Computing Application Server (MCAS or simple MAS)is defined
as a software program which runs in a server and provides the
following functionality:
1. Application level logic that handles business functions involved in a
particular organization and its integration with backend database or
business application systems
2. Presentation services for the Mobile client device (handheld computers,
notebook, PDA, etc). It includes breaking the messages into smaller
chunks, filtering redundant information, and even logically compressing
the data , etc.
3. Transaction services - including multi-threading for heavy volumes and
persistency i.e. recovery across session failures
4. Application programming level interfaces (APIs) with specialized
communications protocols
An application server may be considered as part of a multi-tier
(mostly three tier) architecture. Conventional tiers are:
▪ First tier - A thin client based on handheld devices or a thick
client on a PC - typically a browser-based interface in the Web
context
▪ Middle tier consists of business applications on a set of servers -
communications and business applications
▪ Third Tier - backend legacy data base systems and
mission-critical ERP systems on a large server or mainframe
Mobile Database Management
Mobile Database
Mobile Database is a database that is transportable, portable,
and physically separate or detached from the corporate
database server but has the capability to communicate with
those servers from remote sites allowing the sharing of various
kinds of data.
A Mobile database is a database that can be connected to a
mobile computing device over a mobile network (or wireless
network).
The client and the server have wireless connections.
It will be applicable on different devices like android based
mobile databases, iOS based mobile databases, etc.
Features of Mobile database :
A cache is maintained to hold frequent and transactions so that
they are not lost due to connection failure.
Mobile databases are physically separate from the central
database server.
Mobile databases resided on mobile devices.
Mobile databases are capable of communicating with a central
database server or other mobile clients from remote sites.
With the help of a mobile database, mobile users must be able
to work without a wireless connection due to poor or even
non-existent connections (disconnected).
A mobile database is used to analyze and manipulate data on
mobile devices.
The components of a mobile database environment include:
Corporate database server and DBMS that deals with and
stores the corporate data and provides corporate applications
Remote database and DBMS usually manages and stores the
mobile data and provides mobile applications
mobile database platform that includes a laptop, PDA, or other
Internet access devices
Two-way communication links between corporate and mobile
DBMS.
Limitations :
It has Limited wireless bandwidth.
In the mobile database, Wireless communication speed.
It required Unlimited battery power to access.
It is Less secured.
It is Hard to make theft-proof.
Smart Client
What Does Smart Client Mean?
A smart client is a type of application environment connected to
the Internet that allows server-based operations through the
HTTP connection model.
Smart client is a way to describe enhanced features and client
applications as these types of IT systems evolve. Some
developers describe the smart client as a next-generation set of
systems that evolved from a rich client environment, where
two-tiered setups allowed multiple users to get network
information.
Smart Client Architecture
Components:
Smart clients
Synchronization server
data/content source
may include proxies or gateways
On the client, we have the user interface, the business logic, as
well as a persistent data store. This application communicates
with a back-end data source, often through an intermediate
synchronization server. The communication stream itself can run
either wirelessly or over a wired connection. Depending on the
technology being used, the connection may require an IP-based
network or an additional communication layer for the
synchronization process.
Smart Client Architecture
When building smart client applications you have three options:
Create a client that uses a persistent data store and
synchronization.
Create a client that uses store-and-forward messaging.
Create a client that combines both a persistent data store and
store-and-forward messaging.
Data store
Data store
A data store is a repository for persistently storing and managing
collections of data which include not just repositories like
databases, but also simpler store types such as simple files,
emails, etc.
A database is a series of bytes that is managed by a database
management system (DBMS). A file is a series of bytes that is
managed by a file system. Thus, any database or file is a series
of bytes that, once stored, is called a data store.
Types of Data store
Data store can refer to a broad class of storage systems including:
Paper files
Simple files like a spreadsheet
File systems
Email storage systems (both server and client systems)
Databases
Relational databases, based on the relational model of data
Object-oriented databases. They can save objects of an object-oriented design.
NoSQL databases
Key-value databases
Wide Column Store
Graph databases
Distributed data stores
Directory services
VMware uses the term datastore to refer to a file that stores a virtual machine
Mobile Application
What Does Mobile Application (Mobile App) Mean?
A mobile application, most commonly referred to as an app, is a
type of application software designed to run on a mobile device,
such as a smartphone or tablet computer.
Mobile applications frequently serve to provide users with
similar services to those accessed on PCs.
Apps are generally small, individual software units with limited
function.
This use of app software was originally popularized by Apple
Inc. and its App Store, which offers thousands of applications for
the iPhone, iPad and iPod Touch.
A mobile application also may be known as an app, web app,
online app, iPhone app or smartphone app.
