ANS1:The Data and Process Modelling techniques to develop a logical model and physical model of the process. When we try to make new system, we need first gather information in logical way and then represent in graphical diagram. This model called Logical Model.
A set of DFD (Data Flow of Diagram) provides a logical model that shows what system does, not how it does. DFD have three content. (1)Data Model, (2) Process Model, (3) User Interface.
* DFD Symbol: – It has four symbols for processes, data flows, data stores and entities, exit. DFD Symbol set uses two ways (1) According to Gane and Sarson symbol set and (2) According to Yourdon Symbol set. The most software company apply Gane and sarson symbol to make DFD.*Process Symbol: –
- It symbol represent as rectangle and referred to as black box because we know inputs, outputs and general function of the process but logical part are hidden.
- It is receives input data and produces output that has different content. In typical design like company we need online resource for fetch and sending on word wide .That time we require business logic or business rule which transform the data and produce the output regarding the requirement.
*Data Flow Symbol:·
This is data’s path for moving information from one direction to another direction.
It can be represent one or more data items.·
DFD could not contain following Data flow error.
(1) Spontaneous generation/Miracle: – If there is not input data flow called Miracle process.
(2) Black Hole: – If process has input but not output than called Black Hole.
(3) Gray Hole: – It has one input and one output but if output has no sufficient information than called Gray Hole.
*Data Store Symbol:-·
It is used in a DFD to represent data that the system stores one or more processes at later time.·
Data store shown between the lines and data.
Data store name is plural and consist noun and adjectives.ex Students, products.
Data store connected to a process with a data flow.
*Entity Symbol:·
It is representing by rectangle symbol with 3D dimensional shaded shape.
It is source/sink or external to represent source of data input and output.
Here source means supplies data to system and sink means an entity receives data from system.
External Entity symbol represents something connected to the information system.
*DFD Main Tasks:-
Step 1: Draw a context diagram
Step 2: Draw a diagram 0 DFD
Step 3: Draw the lower-level diagram. *Context Diagram:
- This is the first level view of information system that generates information system.
- It include only one process identify by o and like a black box that heading of whole information system.
- Around single central process we placed the external entities and use data flows to connect the entities to central process.
- In context diagram we could not show internal data store.
- We use unique names and reference number within each set of symbols and process.
*ZERO level DFD:-
- If we want show the detail of the context black box than we need to create ZERO level DFD.
- Here we can show externally processes, data flows, data store.
- Zero Level DFD need to split down further low level DFD.
*Lower-level Diagram:-
· These techniques require to levelling and balancing techniques.
Getting more and more detailed of diagram for show the process is called levelling·
For ensuring properly input and output of data flows require Balancing.
ANS2:The Data and Process modelling concepts are important:
- It is logical model so it will co-operate in business firm and user need.
- This modelling is divided more and more externally design of information system in graphical view. So it is very easy for developer to develop the system more comfortably.
- If it is created then it is time consuming and compress task for developer to develop system.
- It is good when we good mapped to implement new system into old system as per user requirement.
- Modelling is very useful for all characteristics of data element to examine, easier recording, implementing data flow, processes and verifying the data at the developing time.
- Thus the modelling is important objective, responsive, and successive to implement system.
Ans 3: The greatest problem of data and process modelling concepts:(1) It will take more time monthly, yearly to develop model in simpler manner.(2) Developer can not develop system before modelling.(3) The responsive part of creating data and process modelling concepts. Only expert technical persons can develop this model.(4) It is cause of huge mistake when implementing the model. So it needs very responsive tasks.
Ans 4:(1) Firstly we review the system and make start and simple path to make information system.(2) We must be aware about Spontaneous genration, balck holes and Gray holes for developing the model.(3) We must use leveling and balancing techniques for ensuring data flow input and output.(4) We have to create input and output table for finding incoming data flow as input and outgoing data flow as output.(5) We mention of all data flow diagram and data stores that use a particular data element.
