CA214: Systems Analysis

COURSE CONTENT

STRUCTURED SYSTEMS ANALYSIS

Overall Goal: Specify a software system given a set of user requirements

Structured Analysis is useful as it enables you to

deal with possibly overwhelming detail in a modular pictorial fashion.

By using the graphic, pictorial tools of Structured Systems Analysis we can overcome a number of serious problems in the investigation of systems.

SYSTEMS ANALYSIS PROBLEMS

The Systems Analyst finds it hard to learn enough about the business to see the requirements through the user’s eyes. (Users tend to be “Doers” rather than “explainers”).

Users don’t know what is feasible and what isn’t. (Either architecture, software or hardware). There are no models to compare.

Systems Analyst can be Overwhelmed by detail

(Both Business and Technical).

MORE SYSTEMS ANALYSIS PROBLEMS

Narrative (story!) based specifications are frequently very difficult to understand (for both SA and User).

The detail of a specification document written in a way to be sensible to users may not be detailed enough for designers.

The analyst occupies a pivotal position between the user and the designer and needs methods to help.

User ↔ Systems Analyst ↔ Systems Designer

THE SPECIFICATION

If we can make a model of the system we can avoid the problem of the user wanting

to see what they get before they know what they want.

SSADM

· UK Govt. standard.

· Method of organising the analysis and design phases of a project

· We are not directly concerned with project management side.

· It breaks into sets of activities and products
(activities = when & how; products = what)

· 5 core modules in SSADM

1. Feasibility Study

2. Requirements Analysis

3. Requirements Specification

4. Logical Systems Specification

5. Physical Design

SSADM MODULE STAGES

1. Feasibility Study - stage 0 feasibility.

2. Requirements Analysis,
stage 1, Investigation of the current environment
stage 2, business systems options.

3. Requirements Specification
stage 3, Specification of Definition of Requirements.

4. Logical Systems Specification
stage 4, Technical Systems Options
stage 5, Logical Design.

5. Physical design
stage 6, Physical Design

Each stage is composed of a number of steps and SSADM techniques are used within the steps.

TECHNIQUES

We will look at the main SSADM Techniques:

· Business Activity Modelling

· Logical Data Modelling

· Data Flow Modelling

· Function Definition

· Relational Data Analysis
(Normalisation)

· Entity Life History