This January 21, 1975 draft surfaced last month in the boxing of research and management working material from my many years at MIT and SofTech. It underwent considerable further editing, but conveys the easy-going flavor of the approach to Structured Analysis before the rules became so stressed that the reasons became obscured. Both are needed, just as both of the original activities and data, as duals, are needed. Through the SADT SIG, the modem IDEFO version of these venerable ideas will be strengthened and enriched.

Doug Ross, October 23,1994

(No Sub-Title)

The feats of jujitsu seem unbelievable, until you realize that it is based on a science of pressure points and leverage which allow all available force to be applied with maximum effect.

SofTech’s new Structured Analysis is similar. Based on almost twenty years of systematic problem-solving, which earlier made the company a leading practitioner of Software Engineering, Structured Analysis allows each client’s analytic talent to be used with maximum effect.

The problem-solving science behind Structured Analysis is based on the observation that the human mind can cope with any amount of complexity, as long as it is sensibly broken into manageable parts that assemble understandably to make the whole. Structured Analysis training, guidelines, checklists, methods, and notations allow people of all backgrounds to be more effective in understanding and solving problems, and presenting those solutions to others or using them for technical purposes.

Since it is concerned only with the management of complexity, Structured Analysis is equally well-suited to abstract problems such as organization, planning, and project control, as it is to technical areas such as requirements analysis, functional specification, design, production, training, operations, and maintenance. Its powerful methods apply equally well to system problems involving men or machines or computers (both hardware and software) – or any combination of these action agents.

On the surface, Structured Analysis is deceptively simple. Anyone with almost no guidance at all can read and understand a structured analysis model – a neatly-organized sequence of simple "blue print" drawings, with supporting labels and texts, which present a top-down, gradual exposure of more and more detail about some subject of interest. Each diagram expresses just enough new information to be helpful to understanding without being confusing – there never are more that six new component parts on any one diagram. Each new part then is broken again into a few more parts of detail on another diagram –completely – there are no gaps, holes, or hidden complexities. Each diagram connects exactly and completely into the model as a whole – any relevant relation shows clearly and explicitly in the structured set of diagrams.

With Structured Analysis you never try to say everything all at once. That would be confusing. An important subject is treated by several interrelated structured analysis models, each one of which covers one carefully-chosen viewpoint in as much detail as is appropriate. The separate aspects then relate together, using obvious cross-referencing notation so that everything is covered – but with no confusing cross purposes of views. Thus what a thing is is separated from how it is built or how it is to be used or how its construction can be managed. Each viewpoint of the common subject is understood separately, then how the parts go together is understood, and then the whole subject is readily understandable – to anyone.

Each viewpoint is covered by a small structured analysis model, and each model itself includes two basic viewpoints, called the Data Model and the Activity Model. They cover, for the chosen viewpoint, the things (real or symbolic – all are "data") and the happenings (of, to, or between them) that, together, make up the whole reality. Thus for an organizational model the "things" might be people, committees, departments, jobs, memos, and manuals, while the "happenings" are their actions and interactions to achieve the objectives of the organization. For a computer program or an entire data processing system, data and activities clearly correspond respectively to the numbers, forms, databases, etc. and the instructions, subroutines, or system functions. For manufacturing, parts and production processes, whether manual or automatic, fit the same pattern. With the universal leverage point of both data and activities, any subject can be made understandable by Structured Analysis.

The "blue print" drawing conventions of Structured Analysis are completely universal – they apply for any subject, any viewpoint, any level of abstraction, or any level of detail – and they apply equally well to data or activity diagramming. Thus users of Structured Analysis need to become familiar with only one mode of expression for all their purposes. Structured Analysis notation is simplicity itself, and is a natural extension of our natural language. People can obtain a reasonable understanding of Structured Analysis diagrams with no explanation at all. Brief training in the extraction of total meaning from the graphic language deepens understanding, but even without it, communication with busy executives is effective.

The part/whole, top-down decomposition of Structured Analysis is closely related to the universally-recognized notion of rational exposition captured in the topic outline method of technical writing. By its organization into volumes, chapters, sections, subsections, paragraphs, topic sentences, subjects, and predicates, good technical writing also presents complex ideas in understandable form. Structured Analysis takes this tested approach (without change) and immeasurably enhances its power by embedding it in a graphic syntax (deceptively simple in form) so that the constraining relations between the natural-language topics are explicitly shown. Structured Analysis notation is a combined graphic, text, and cross-reference language of unparalleled expressive power precisely because it is a natural extension of our natural language. Structured Analysis itself is the mental discipline and body of tested guidelines and rules that allow that language to be used both to unravel well-structured solutions to problems and to communicate those on-paper solutions to others.