1. Information Systems Development (ISD) Systems Development Life Cycle
Overview of Analysis Phase
Overview of Design Phase
Information Systems Design

2. Information Systems Development (ISD)
A logical series of development phases followed in an organisation to conduct all the steps necessary to analyse, design, implement & maintain information systems.
These logical series of development phases - known as System Development Life Cycle (SDLC).

3. Systems Development Life Cycle (SDLC)
Scope & objectives
Feasibility
Analysis
Time
Waterfall Model
Proven approach
Lacks flexibility
Time lag
Ensures points of review
Design
Implement
Maintain
Review

4. Alternative Approaches (1)
Waterfall SDLC with iterations:
Scope & objectives
Feasibility
Analysis
Design
Implement
Maintain
Review

5. Alternative Approaches (2)
Beer mat and hack.
Prototyping / Rapid Application Development.
Uses a different SDLC
System developed in smaller units
Iterative
Less time lag
User participation
Analysis
Review
Design
Code

6. Alternative Approaches (4)
Spiral model includes best features of both the classic Waterfall SDLC and the Prototyping approach.
Planning
Risk Analysis
The Spiral Model - an iterative (evolutionary) system development life cycle developed by Boehm (1988) which incorporates risk assessment.
Developed in recognition of the fact that systems development projects tend to repeat the stages of analysis, design and code as part of the prototyping process.
Model closely related to RAD, as it implies iterative development with a review possible after each iteration or spiral - which corresponds to the production of one prototype or incremental version.
Development
Evaluation

7. Alternative Approaches (5)
Each spiral consists of four main activities:
Planning: setting project objectives; defining alternatives; further planning on the next spiral; etc.
Risk Analysis: analysis of alternatives & the identification & solution of risks.
Development: designing, coding and testing etc. in increments.
Evaluation: user evaluation of each spiral and then the final product.

8. SDLC Stages and Deliverables (1)
Terms of Reference
Feasibility Report
Requirement specification, Physical & Logical models
Logical models of required system, physical design and detailed design documentation
Scope & Objectives
Feasibility
Analysis
Design

9. SDLC Stages and Deliverables (2)
Code - program documentation
Test - Test plans from unit to system & acceptance testing
Install - system changeover, installation of hw/sw, user & system documentation and training
Maintenance procedures
Evaluation report
Implementation:Code, Test & Install
Maintain
Review

10. Analysis Analysis - Overview (1) Scope & Objectives
PRL RC current system’s
DFDs
LDS
I/Os
Process desc.
Feasibility
Analysis
Design
Time
Implement
Maintain
Requirements
Specification
of req.System
Review

11. Problem Requirements List Data Store Entity Cross Reference
Analysis - Overview (2)
Current Physical
DFDs
Current Logical
Current System
LDS
Problem Requirements List
(Requirements Catalogue)
Logicalisation
Data Store Entity Cross Reference
PHYSICAL ANALYSIS
LOGICAL ANALYSIS

12. Analysis - Overview (3)
Analysis - gathering & documentation of information about the current system & the required system.
To achieve this - a number of techniques are used.
Problem Requirement List feeds into Requirements Catalogue: contain information about current problems & future requirements
(logical: functional & physical: non-functional)
Data Flow Diagrams (Processing): contain information about the processing, inputs and outputs and data stores to be accessed.

13. Analysis - Overview (4)
Logical Data Structures (Data): contain information about the groups of data (entities) and their relationships.
Input\Output Descriptions: contain information about data that flows into and out of the system.
Process Descriptions: contain information about how the processes actually work & these can be specified using various techniques
(e.g. Structured English, Decision Tables & Decision Trees).

14. Analysis - Physical & Logical
Physical analysis includes all physical aspects
e.g. Filing cabinets, Locations, (Who, When, Where, etc).
Physical analysis become logical when all the physical aspects are removed by logicalisation.
Therefore there are 2 versions of the DFDs current physical and current logical.

15. Analysis - Data & Processing
DFDs model information about the processing in the current system.
LDS models information about the data in the current system.
Data & Processing are two separate but essential components of an Information System.

16. Analysis - Techniques
The techniques used to perform analysis are taken from Structured Systems Analysis and Design Methodology (SSADM).
There are other techniques and ways of combining them in order to perform analysis.

17. Design Feasibility Analysis Implement Time Maintain Review
Design - Overview (1)
Scope & Objectives
Feasibility
Analysis
Design
Implement
Time
Maintain
Review

18. Design Design - Overview (2) System Specification of req. System
PRL RC current system’s
DFDs
LDS
I/Os
Process desc.
Requirements
Specification
of req. System
Design
System
Specification
of req. System

19. Required Logical Design RequiredPhysical Design
Design - Overview (3)
Design
Required Logical Design
RequiredPhysical Design

20. Design - Overview (4)
Logical Design: gives a detailed logical definition of the required system.
Physical Design: takes the products of the logical design and produces specifications for the target hardware and software.

21. Design - Overview (5) Logical Design:
No reference made to any technical environment.
Capable of implementation on a variety of platforms.
Act as a model of how the system will satisfy the user requirements.
Reflect underlying business rules & activities rather than physical constraints.

22. Design - Overview (6)
Logical Design - blueprint is the delivered product of the required system.
It includes the following:
Requirements Catalogue
Required system DFDs
Required system LDS
Relational Data Analysis (normalised set of tables and rationalised set of tables)

23. Design - Overview (7) Physical Design:
Logical design translated into a physical design based on the technical environment selected, e.g. platform, programming language, database etc.
Produces program specifications, physical files or database definitions and user interfaces for a selected target hardware & software.

24. Design - Overview (8)
Physical design includes contents of the following components;
Data design - (requirements for data to be stored in a database)
Outputs design - (reports, displays)
Inputs design - (forms, screens, dialogues)
Programs design - (structure of programs to collect, transform & output data)

25. DESIGN Design Overview (9) Requirements Catalogue I/O Data Design
Descriptions
Data Design
DESIGN
Interface
Design
Program Design
System Objectives: Review of Analysis, Requirements Specification, Design Objectives & Constraints.
Data Design - Design of files and databases.
I/O Design - Inputs & Output descriptions, Report & Form Design.
Interface Design - Screen Design: Menus, Dialogues, etc.
Process Design - Program design using structured English, etc.
System Changeover Strategies - How to move from old to new system
Documentation - System & User documentation.
System
changeover
strategies
Documentation:
System & User

26. Physical and Logical Models
Analysis
Design
Current
Logical
Required
Logical
Current
Physical
Required
Physical