Section 02 Systems Documentation 1

02 Systems Documentation

And Franchise Colleges

By MANSHA NAWAZ

Section 02 Systems Documentation 2

Learning Aims– to understand the documentation requirements

for computing projects

– systems development activities

– to be able to draw up a Terms of Reference for a

proposed small scale computerised system

Section 02 Systems Documentation 3

DOCUMENTATIONOVERVIEW

Section 02 Systems Documentation 4

Developing Computer Systems

• TEAM – share system development tasks– Size of development team– Size and scope of project– Skill & experience of the team ….

• Documentation used to communicate.

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Early Systems Development

First systems • no method or special

techniques– used flow charts– used english text

• experience & rule of thumb

Growth period• systems became

– larger– more complex– more numerous

• problems arose– late– over budget– bugs

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The Solution

• Needed was a way to– handle lots of detail– produce reports specific to stage of

development– allow communication analyst - customer

• Structured Methodologies– Yourdon, DeMarco, Gane & Sarson– later SSADM, Waterfall, etc

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Structured Methods

• ordered set of related techniques

• specific to needs of the various stages

• mainly graphical models but supported with text

• manageable

• training & guidance available

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STRUCTURED METHODOLOGIES

– used to document all systems to a universally accepted defined standards

• Documentation standards – use the same tools• Speak the same language - use the same tools

• Structured Methodology tool of interest : – Computer Aided Software Engineering Tools &

Techniques (CASE)

Please Note

There are many different CASE Tools and Techniques available

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The Techniques

See Supplement 02 Computer Aided Software Engineering

Tools and Techniques(CASE)

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CASE Tools and Techniques of interest

• Data Flow Diagrams – context diagram, top-level dfd, explosions

• Data Dictionaries – data description, process logic

• Normalisation– Design technique for database tables

• Entity Relationship Diagrams Database Development

– Modelling technique for database tables

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Graphical models

• short precise compared to english narrative

• abstract, focus on essential detail

• hierarchical, levels of detail

• partitionable, view different parts

• minimally redundant, easy to change

• transparent, see ‘reality’ not technology

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Computers and Reality

• The real world consists of people, places, forms, letters, documents

• Non of these exist within the computer• Our models reflect this by showing a

LOGICAL view of the system• The models (dfds) show what happens

to data about things in the system & not what happens to the actual things

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For the purposes of this module we are going to restrict our SYSTEMS METHODOLOGY to utilise the following :

CASE Tools and Techniques of interest

• Data Flow Diagrams – context diagram & Events List

– top-level dfd

– low-level dfd’s (explosions)

• Data Dictionaries – Data Description

– Process Descriptions

• Normalisation

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For the purposes of this module we are going to restrict our SYSTEMS METHODOLOGY to utilise the following :

Systems Documentation

• Analysis Specification

• Design Specification

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Document : Analysis Specification – Terms Of Reference lecture 02

• Statement of Purpose• Requirements• Functions• Constraints

– Context Diagram & Events List lecture 03

– Top-Level Data Flow Diagram lecture 04 lecture 05

– Low-Level Data Flow Diagrams lecture 06 lecture 07

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– Data Dictionary lecture 08

• Data Stores - Structures & Elements lecture 08

• Data Flow - Structures & Elements lecture 08

• Data Stores and Flow Usage lecture 09

• Process Descriptions lecture 10

– NORMALISATION lecture 11

• Database Tables derived from Data Store Descriptions

Document : Design Specification

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DOCUMENTATIONIN DETAIL

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For the purposes of this module we are going to restrict our Terms of Reference to the following sections:

Terms Of Reference• Statement of Purpose• Requirements• Functions• Constraints

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• Is an introduction to the project environment• Short English narrative highlighting the customer

background and current situation• Description of the area to be investigated

– what is inside the system boundary

• Business activities• System environment - physical area• Organisation & structure• Systematically refined and added to as we gain

more awareness of the system environment

TERMS OF REFERENCE

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• Short English narrative highlighting what the proposed system should do

• Systematically refined and added to as we gain more awareness of the system

STATEMENT OF PURPOSES

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To achieve its purpose the proposed system will have to perform a variety of operations– record sequentially in a numbered list– each a statement of a required function– include general must do things– no detail of how to do – no detail of the overall structure

• Systematically refined and added to as we gain more awareness of the system

Functional Requirements

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CONSTRAINTS

Customers often place other constraints that have nothing to do with the system function. – Non-functional Requirements– delivery time– run on specified hardware platform– use of specific language/software– record sequentially in a numbered list

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Summary• Stages involved in Systems Analysis

• Stages involved in Systems Design

• What CASE tools we will use

• What documentation we will produce

• Establish Terms of Reference – Terms Of Reference

• Statement of Purpose• Requirements• Functions• Constraints

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Self Study

Self Study• Review the lecture• Complete task 2a & b in the workbook• can you achieve the aims stated in slides 2?

• Check Further Reading Section following the next slide

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Further Reading

Supplement 02

Systems Theoryonline only

available online

Section 02 Systems Documentation 26

Further Reading

Supplement 02

Establishing User Requirementonline only

available online

Section 02 Systems Documentation 27

Further Reading

Supplement 02

Rich Picture.doc

available online

Section 02 Systems Documentation 28

References

• Hoffer, J.A. et.al. “Modern Systems Analysis & Design” 3rd Ed. Addison-Wesley 2002 Ch1, pp11-15, Ch2-3 Ch4 pp93-119

• Bennett, S. et. al. “Object-Oriented Systems Analysis & Design using UML” McGraw-Hill 1999 cCh1 pp18-20, Ch3 pp55-60, Ch11 pp245-7

• Parkin, A. (1987) “Systems Analysis” Edward-Arnold• Reading:

– Bennett et al, Chapter 5– Hoffer et al, Chapter 7 pp 202–237

• Reference source:– David Budgen, Software Design, Addison Wesley, 1993