Ict a Level - Module 4 - Ssadm

ICT A Level - Module 4 - SSADM

Homework - SSADM Sheet

Explain why systems analysis should be employed when developing a computer system rather than just "knocking up" a system from scratch.

SSADM is a systems approach to the analysis and design of information systems. Short for Structured Systems Analysis and Design Method, a set of standards developed in the early 1980s for systems analysis and application design widely used for government computing projects in the United Kingdom. SSADM uses a combination of text and diagrams throughout the whole life cycle of a system design, from the initial design idea to the actual physical design of the application.

SSADM uses a combination of three techniques:

Logical Data Modeling -- the process of identifying, modeling and documenting the data requirements of the system being designed. The data is separated into entities (things about which a business needs to record information) and relationships (the associations between the entities).

Data Flow Modeling -- the process of identifying, modeling and documenting how data moves around an information system. Data Flow Modeling examines processes (activities that transform data from one form to another), data stores (the holding areas for data), external entities (what sends data into a system or receives data from a system, and data flows (routes by which data can flow).

Entity Behavior Modeling -- the process of identifying, modeling and documenting the events that affect each entity and the sequence in which these events occur.

Each of these three system models provides a different viewpoint of the same system, and each viewpoint is required to form a complete model of the system being designed. The three techniques are cross-referenced against each other to ensure the completeness and accuracy of the whole application.

SSADM application development projects are divided into five modules that are further broken down into a hierarchy of stages, steps and tasks:

Feasibility Study -- the business area is analyzed to determine whether a system can cost