1a.
A data model is a picture or description which shows how data
is to be arranged to serve a specific purpose.
b. Data Modelling is the process of structuring and organizing data. The
data structures are then typically implemented in a database management
system. In addition to defining and organizing the data, data modelling may
also impose constraints or limitations on data placed within the structure.
ci. Flat file model: A flat data is a type of database that stores
data in a single table. Flat file databases are generally in plain-
text form, where each line holds only one record. The fields in the
record are separated using delimiters such as tabs and commas.
ii. Hierarchical model: In this model, data is organized into a
tree like structure. The data is stored as records which are
connected to one another through links. In a hierarchical model,
each child record has only one parent, whereas each parent
record can have one or more children. At the top of hierarchy
there is only one entity which is called Root. In order to retrieve
data from a hierarchical database the whole tree needs to be
traversed starting from the root node.
iii. Network model: In the network model, data records are
organized in a graph, in which some records can be accessed
through several paths. This model organizes data using two
fundamental constructs, called records and sets. Records contain
fields, and sets define one-to-many relationships between
records: one owner, many members.
iv. Relational model: In this model, data record is organized
in two-dimensional tables called relations. The tables or relations
are related to each other. Each table is made up of rows and
columns and a table stores records about a particular subject.
Relational data models are used in IBM’s DB2, Informix, Oracle,
Sybase, Paradox, FoxBase, Teradata).
