Assignment # 01
Q#01:
State the significance of DFDs in the process of Database designing. (5)
Solution:
DBMS Development:
There are some tools used to describe a design process. These also
help the designers of database system to mutually agree on a specific
design.
If there is no standard tool for designing a specific DBMS then every
designer will have his own design for developing that specific design.
This can create misunderstanding or conflict among the designs for
that specific DBMS.
So, DFD is that standard tool that can be used to resolve this
conflict among different designs and to get utmost the same result by
different designers.
Significance of DFDs in the process of Database development:
DFD are used to design data centric applications. They follow the data
through entry, storage, retrieval transformations and output. Storage
and retrieval are where the database comes in. You can use the DFD to
design the schema for the most efficient use of the data in the
context of the application. Of course this is simplified but this is
the general idea.
• DFDs are most important and common tools for designing a database system.
• It presents a system diagrammatically and expresses details of the
different DFD levels.
• It shows the flow of data among various processes / levels.
• These are very simple. DFDs hide the complexities of the system.
• These are easy to understand and create links among different levels
and process of the information flow.
DFDs represent the functions a system performs hierarchically,
starting with the highest-level functions and moving through various
layers or levels of sub-functions. As a modeling technique, DFDs are
useful for performing a structured analysis of software problems,
allowing developers to spot and pinpoint issues in software
development.
It is, therefore, important and common because of its simple graphical
representation. It has various symbols that are simple and easy to
understand. These symbols make the DFD more elegant. They're often
used to model software and to show the flow of data in a system.
Following are some common components of DFDs:
There are some components of DFDs which enhances the importance of it
in a system:
Dataflow symbol_ its purpose in DFDs is to express the flow of
information form one entity to another.
Data Store_ data store is for the storage of data. It is for the
permanent store of data in the system. It is represented by a
rectangle shape open on right width and left one is drawn with double
line.
Processes_ processes are expressed with ovals or rounded rectangles.
When data is transformed from one form into a processed form.
DFD Process_ these are numbered for showing the existence of DFDs at a
certain level in the system.
External Entities_ these are interacting with the system in two
different ways. They may be either receiving data from the system or
may be producing data for the system.
Collector_ it is used to show the convergence of data to a single point.
Separator_ this symbol is used for separating data from a single
source to multiple sinks.
Ring Sum Operator_ this operator is used when data from a single
source process flows to one of the required sinks.
AND Operator_ this operator is used when data from a single source
process must flow to all of the required sinks.
Q#02:
Draw a Context and level 0 Data Flow Diagrams of mobile SIM
registration System. Guidelines are given below. (3+7)
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