[FONT="]Q 1. State the significance of DFDs in the process of Database designing.[/FONT][FONT="] [/FONT][FONT="](5)[/FONT] [FONT="]Q 2. Draw a Context and level 0 Data Flow Diagrams of mobile SIM registration System. Guidelines are given below[/FONT][FONT="]. (3+7)[/FONT][FONT="] [/FONT] [FONT="]Guidelines / Requirements:[/FONT] [FONT="]The context level diagram must contain a major process and external entities.[/FONT]
[FONT="]Level 0 diagram must consist of major functions and should work as follows: [/FONT]
[FONT="] [/FONT] Ø There should be 3 streams, or flows of data.
(i) The customer request to buy a number of his choice, system check the availability of number and get the details of customer for SIM card registration.
(ii) Bill will be generated on behalf of SIM card and customer detail.
(iii) And finally customer gets the SIM after payment in cash.
[FONT="] [/FONT] [FONT="]Before Starting you should study and understand:[/FONT][FONT="] [/FONT] · [FONT="]Significance of[/FONT][FONT="] [/FONT][FONT="]DFD[/FONT]
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)
