the systems life cycle: analysis 2

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The Systems Life Cycle: Analysis 2 Data flow & information requirements

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Data flow & information requirements. The Systems Life Cycle: Analysis 2. Objectives:. Establishing IPSO Recording information about the existing system Identifying the problems with the system Identifying User & Information requirements of the new system - PowerPoint PPT Presentation

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Page 1: The Systems Life Cycle:  Analysis 2

The Systems Life Cycle: Analysis 2

Data flow & information requirements

Page 2: The Systems Life Cycle:  Analysis 2

Objectives:

Establishing IPSO Recording information about the

existing system Identifying the problems with the

system Identifying User & Information

requirements of the new system Identifying HW & SW for a new

system.

Page 3: The Systems Life Cycle:  Analysis 2

So far….

Our analyst has collected information about the current system using questionnaires, observation, interviews and examining documents.

What happens next?

Page 4: The Systems Life Cycle:  Analysis 2

Step 2: Need to identify all the

inputs, processing & outputs in the existing system.

How?

Page 5: The Systems Life Cycle:  Analysis 2

1: Examination of documents

This allows the analyst to establish which documents relate to information coming IN to the system, and which relate to information going OUT.

Page 6: The Systems Life Cycle:  Analysis 2

What happens to this information?

The analyst uses this knowledge to produce his own documentation of the system which helps him understand the system properly.

Page 7: The Systems Life Cycle:  Analysis 2

Each section…

….needs to be examined to see the specific inputs, processes & outputs.

What would be the inputs of a payroll system?

The processes? The outputs?

Page 8: The Systems Life Cycle:  Analysis 2

2 : Recording information about the current system All results of fact-finding

must be recorded Accurate records are

vital – why? Because the system will

evolve Other analysts &

programmers will need to develop the system even further at some point in the future.

Page 9: The Systems Life Cycle:  Analysis 2

How do we record the flow of data?

Data flow diagrams These are a graphical

method of recording the inputs, processing & outputs that have been identified.

Page 10: The Systems Life Cycle:  Analysis 2

Flow charts vs DFDs

Flow charts show the control flow of the program

DFDs show how the data flows around the entire system

Page 11: The Systems Life Cycle:  Analysis 2

3 : DFDS….

Data flow diagrams illustrate how data is processed by a system in terms of inputs and outputs.

Have four components: Terminators Processes Flow arrows Stores

Page 12: The Systems Life Cycle:  Analysis 2

An example

Process

order

Customers

Orders

Rejected Orders

Orders

Invoices Invoic

e data

Order In

formati

on

Page 13: The Systems Life Cycle:  Analysis 2

An explanation

Customers A Terminator - someone or something outside the system (eg a customer or a supplier)

Invoices Data stores – where stored on paper or on a computer

Data flow. It is important that the direction of the flow is accurately recorded.

Process

orderProcess order

Page 14: The Systems Life Cycle:  Analysis 2

Different levels of DFDs

Level 0 Very generalised Shows terminators linked

to current system eg 0Customers

Order Processing system

Customers

Page 15: The Systems Life Cycle:  Analysis 2

Different levels of DFDs

Level 1: Many more processes More detail Process boxes for both

receiving orders and for producing invoices 1

Page 16: The Systems Life Cycle:  Analysis 2

Different levels of DFDs

Level 2: These show all aprts of

the level 1 diagram in much more detail 2

Page 17: The Systems Life Cycle:  Analysis 2

DFDs:

Represent the way that data flows around the existing (old) system

Page 18: The Systems Life Cycle:  Analysis 2

System flowcharts

May be used, but generally are found in the design stage.

Represent the new system – the one that is going to be designed & implemented.

Page 19: The Systems Life Cycle:  Analysis 2

4 : Identifying problems with the current system DFDs help the analyst to

identify problems or weaknesses within the current system: Eg data duplication Job duplication Unnecessary steps

Why is it necessary to identify these problems?

Page 20: The Systems Life Cycle:  Analysis 2

5 : Identifying suitable hardware & software for the new system

DFDs help the analyst decide on: Appropriate methods of

input Approximate processor

speed & memory Size & number of

storage devices Quantity & format of

output

Page 21: The Systems Life Cycle:  Analysis 2

6: Identifying the user & information requirements The new system MUST meet the

needs of the people who will use it So – the analyst needs to know

exactly what job each person does and what their requirements are.

He can the produce a Requirements Specification – a list of features of the system that are required.

Page 22: The Systems Life Cycle:  Analysis 2

Analysis Summary

Step 1 : collecting information on how the current system works

Step 2 : Establishing inputs, processes & outputs

Step 3 : recording information Step 4 : Identifying problems Step 5 : Identifying suitable hardware &

software Step 6 : Identifying user & information

requirements