Wells Computer Consultants Ltd

Structured Systems Analysis and Design Method (SSADM) is the approach adopted by Wells Computer Consultants for Analysis, Specification of Requirements and Logical Design. By involving business users at each project stage the risk of producing the 'wrong' system is reduced considerably and informed business decisions on how or if a project should proceed can be taken. The stages and 'products' required can be tailored to accommodate the circumstances of each project. Completeness and consistency of the 'products' at the end of each project stage can be checked at formal reviews. The stages for an SSADM project are as follows:

Consider a project such as this must have taken many years in the planning and design. It was time well spent when you consider the end result. Consult WCCL for your analysis and design requirements. info@wccl.co.uk

• Project Initiation and Feasibility Study. Project Initiation must define the objectives to be achieved. The Feasibility Study is a 'high level' examination of the options, costs, benefits and risks for the project and the resultant information system for the business. For small, low budget, projects or projects where there is no other option a Feasibility Study may not be required.

• The Analysis of Requirements establishes the logic of the current business system(s) (if a system exists, manual or computer), other business requirements, problems with existing system(s) and the Business Options to address the requirements.

• The Specification of Requirements defines the Logical Data Model (LDM), the Data Flow Model (DFM) and verifies the completeness and consistency of the models by the techniques of Entity Event Modelling and Access Path Analysis. This provides three logical views of the required system, all of which must reconcile. The LDM specifies the information that is to be held, how it is logically grouped into entities (e.g. an order is an entity because it represents a group of information important to the order) and the relationships that exist between the sets of data. The DFM identifies the events that the system must recognise, the information that must be available as a result of the event and the processing that must occur to incorporate the data in the LDM. The Entity Event Modelling verifies that for each entity, there are events which create, modify and delete instances of the entity and that the information held at any time and the sequence in which events occur is consistent with other entities e.g. in a sales order processing system orders would not be expected to exist without a customer.

• The purpose of the Technical System Options is to examine and agree which is the 'best' option for implementation of the required system. The criteria which should be considered in the decision making process are:
  • a) the physical environment both hardware and software and its compatibility with existing systems.
  • b) package software or custom built in house or by an external developer.
  • c) functionality that can be supported in the proposed environment.
  • d) development tools for an in house custom built system.
  • e) development and implementation plans with resource requirements and time scales.
  • f) costs for development, implementation and running.
  • g) impact of the system on the business, the benefits, advantages and disadvantages.
  • h) service levels, security and disaster recovery
  • i) operational changes, staffing and staff training.

• The Logical Design Stage is relevant for a custom built system. It is important that a design is produced sufficient that business users and developers can understand the interpretation of the logic of the Specification of Requirements. The design stage builds the menu structures, the grouping and sequence in which data is entered for a process (not screen layout) and the detailed processing, for update and retrieval, in a diagrammatic form to support the Entity Event Modelling and the Access Path Analysis. Modern Rapid Application Development (RAD) Tools provide the means to accomplish these tasks quickly and take menu structures and data acquisition through to screen design without the intermediate SSADM stage.

• The product of the Physical Design stage is an optimised physical design for the selected physical environment. It is the last of the SSADM stages because, beyond this point, the physical environment dictates the development stages required. Physical Design includes:
  • a) mapping and optimisation of the LDM into the selected database.
  • b) completion of physical screen and report design.
  • c) error handling for input and output - syntax and media.
  • d) record/row locking sequences.
  • e) controls on data capture.
  • f) help messages.
  • g) common processing - reuse of modules.
  • h) input/output formats for printers, communications and data transfer.

For assistance with analysis and specification of your business requirements and design of your systems contact Wells Computer Consultants Ltd. Click on the email address below.