engineering

Structured systems analysis and design method

Structured systems analysis and design method is a engineering topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Structured systems analysis and design method rather than just read about it. In short: Structured systems analysis and design method (SSADM) is a systems approach to the analysis and design of information systems. SSADM was produced for the Central Computer and Telecommunications Agency, a UK government office concerned with the use of technology in government, from 1980 onwards.

Key takeaways

Structured systems analysis and design method belongs to engineering; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Structured systems analysis and design method to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Structured systems analysis and design method from memory before moving on to harder problems.

Reference excerpt

Structured systems analysis and design method (SSADM) is a systems approach to the analysis and design of information systems. SSADM was produced for the Central Computer and Telecommunications Agency, a UK government office concerned with the use of technology in government, from 1980 onwards.

Overview SSADM is a waterfall method for the analysis and design of information systems. SSADM can be thought to represent a pinnacle of the rigorous document-led approach to system design, and contrasts with more contemporary agile methods such as DSDM or Scrum. SSADM is one particular implementation and builds on the work of different schools of structured analysis and development methods, such as Peter Checkland's soft systems methodology, Larry Constantine's structured design, Edward Yourdon's Yourdon Structured Method, Michael A. Jackson's Jackson Structured Programming, and Tom DeMarco's structured analysis. The names "Structured Systems Analysis and Design Method" and "SSADM" are registered trademarks of the Office of Government Commerce (OGC), which is an office of the United Kingdom's Treasury.

History The principal stages of the development of Structured System Analysing And Design Method were:

1980: Central Computer and Telecommunications Agency (CCTA) evaluate analysis and design methods. 1981: Consultants working for Learmonth & Burchett Management Systems, led by John Hall, chosen to develop SSADM v1. 1982: John Hall and Keith Robinson left to found Model Systems Ltd, LBMS later developed LSDM, their proprietary version. 1983: SSADM made mandatory for all new information system developments 1984: Version 2 of SSADM released 1986: Version 3 of SSADM released, adopted by NCC 1988: SSADM Certificate of Proficiency launched, SSADM promoted as 'open' standard 1989: Moves towards Euromethod, launch of CASE products certification scheme 1990: Version 4 launched 1993: SSADM V4 Standard and Tools Conformance Scheme 1995: SSADM V4+ announced, V4.2 launched 2000: CCTA renamed SSADM as "Business System Development". The method was repackaged into 15 modules and another 6 modules were added.

SSADM techniques The three most important techniques that are used in SSADM are as follows:

Logical Data Modelling The process of identifying, modelling and documenting the data requirements of the system being designed. The result is a data model containing entities (things about which a business needs to record information), attributes (facts about the entities) and relationships (associations between the entities). Data Flow Modelling The process of identifying, modelling 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 Event Modelling A two-stranded process: Entity Behavior Modelling, identifying, modelling and documenting the events that affect each entity and the sequence (or life history) in which these events occur, and Event Modelling, designing for each event the process to coordinate entity life histories.

Stages The SSADM method involves the application of a sequence of analysis, documentation and design tasks concerned with the following.

Stage 0 – Feasibility study In order to determine whether or not a given project is feasible, there must be some form of investigation into the goals and implications of the project. For very small scale projects this may not be necessary at all as the scope of the project is easily understood. In larger projects, the feasibility may be done but in an informal sense, either because there is no time for a formal study or because the project is a "must-have" and will have to be done one way or the other. A data flow Diagram is used to describe how the current system works and to visualize the known problems. When a feasibility study is carried out, there are four main areas of consideration: Technical – is the project technically possible? Financial – can the business afford to carry out the project? Organizational – will the new system be compatible with existing practices? Ethical – is the impact of the new system socially acceptable? To answer these questions, the feasibility study is effectively a condensed version of a comprehensive systems analysis and design. The requirements and usages are analyzed to some extent, some business options are drawn up and even some details of the technical implementation. The product of this stage is a formal feasibility study document. SSADM specifies the sections that the study should contain including any preliminary models that have been constructed and also details of rejected options and the reasons for their rejection.

Stage 1 – Investigation of the current environment The developers of SSADM understood that in almost all cases there is some form of current system even if it is entirely composed of people and paper. Through a combination of interviewing employees, circulating questionnaires, observations and existing documentation, the analyst comes to full understanding of the system as it is at the start of the project. This serves many purposes (Like examples?).

Stage 2 – Business system options Having investigated the current system, the analyst must decide on the overall design of the new system. To do this, he or she, using the outputs of the previous stage, develops a set of business system options. These are different ways in which the new system could be produced varying from doing nothing to throwing out the old system entirely and building an entirely new one. The analyst may hold a brainstorming session so that as many and various ideas as possible are generated. The ideas are then collected to options which are presented to the user. The options consider the following:

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Structured systems analysis and design method

Start with the simplest possible case. Write down what Structured systems analysis and design method claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In engineering, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Structured systems analysis and design method before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Structured systems analysis and design method ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Structured systems analysis and design method

In research: Structured systems analysis and design method appears in engineering research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Structured systems analysis and design method in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Structured systems analysis and design method is common in secondary-school and first-year university syllabi. It links to neighbouring topics Information systems, Software design, Systems analysis, so understanding it makes those chapters shorter.
In everyday life: Look for Structured systems analysis and design method outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Structured systems analysis and design method in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Structured systems analysis and design method means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Structured systems analysis and design method out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Structured systems analysis and design method in simple terms?

Why does Structured systems analysis and design method matter?

Because it connects several engineering ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Structured systems analysis and design method?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Structured systems analysis and design method.