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{{nofootnotes|date=May 2010}}
'''Structured
== Overview ==
SSADM is a [[Waterfall model|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 software development|agile]] methods such as [[Dynamic Systems Development Method|DSDM]] or [[Scrum (development)|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 [[
The names "Structured Systems Analysis and Design Method" and "SSADM" are [[trademark|registered trademarks]] of the [[Office of Government Commerce]] (OGC), which is an office of the United Kingdom's Treasury.<ref>{{cite web
|url = http://www.ogc.gov.uk/intellectual_property_annex_1.asp
|title = OGC
|publisher = Office of Government Commerce (OGC)
|accessdate = 2010-12-17}}</ref>
== History ==
The principal stages of the development of SSADM were:<ref>{{cite web |url = http://www.dcs.bbk.ac.uk/~steve/1/sld005.htm |title = History of SSADM |work = SSADM
* 1980: Central Computer and Telecommunications Agency (CCTA) evaluate analysis and design methods.
* 1981: Learmonth & Burchett Management Systems (LBMS) method chosen from shortlist of five.
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== SSADM techniques ==
The three most important techniques that are used in SSADM are:
; Logical
: This is the process of identifying, modeling and documenting the data requirements of the system being designed. The data are separated into entities (things about which a business needs to record information) and relationships (the associations between the entities).
; Data Flow Modeling
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== Stages ==
The SSADM method involves the application of a sequence of analysis, documentation and design tasks concerned with the following.
=== Stage 0
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 not time for a formal study or because the project is a “must-have” and will have to be done one way or the other.
When a feasibility study is carried out, there are four main areas of consideration:
*Technical
*Financial
*Organizational
*Ethical
To answer these questions, the feasibility study is effectively a condensed version of a fully blown systems analysis and design. The requirements and users are analyzed to some extent, some business options are drawn up and even some details of the technical implementation.
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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
This is one of the most important stages of SSADM. The developers of SSADM understood that though the tasks and objectives of a new system may be radically different from the old system, the underlying data will probably change very little. By coming to a full understanding of the data requirements at an early stage, the remaining analysis and design stages can be built up on a firm foundation.
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In the process of preparing the models, the analyst will discover the information that makes up the users and requirements catalogs.
=== Stage 2
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.
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The users and analyst together choose a single business option. This may be one of the ones already defined or may be a synthesis of different aspects of the existing options. The output of this stage is the single selected business option together with all the outputs of stage 1.
=== Stage 3
This is probably the most complex stage in SSADM. Using the requirements developed in stage 1 and working within the framework of the selected business option, the analyst must develop a full logical specification of what the new system must do. The specification must be free from error, ambiguity and inconsistency. By logical, we mean that the specification does not say how the system will be implemented but rather describes what the system will do.
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To produce the logical specification, the analyst builds the required logical models for both the [[Data flow diagram|data-flow diagrams]] (DFDs) and the [[Entity-relationship model|entity relationship diagrams]] (ERDs). These are used to produce function definitions of every function which the users will require of the system, entity life-histories (ELHs) and effect correspondence diagrams, these are models of how each event interacts with the system, a complement to entity life-histories. These are continually matched against the requirements and where necessary, the requirements are added to and completed.
The product of this stage is a complete
'''*the updated
*the updated
*the
:*user role/function matrix
:*function definitions
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Though some of these items may be unfamiliar to you, it is beyond the scope of this unit to go into them in great detail.
=== Stage 4
This stage is the first towards a physical implementation of the new system. Like the Business System Options, in this stage a large number of options for the implementation of the new system are generated. This is honed down to two or three to present to the user from which the final option is chosen or synthesized.
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The output of this stage is a chosen technical system option.
=== Stage 5
Though the previous level specifies details of the implementation, the outputs of this stage are implementation-independent and concentrate on the requirements for the human computer interface. The logical design specifies the main methods of interaction in terms of menu structures and command structures.
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*Data catalog
*Required logical data structure
*Logical process model
* Stress & Bending moment.
=== Stage 6
This is the final stage where all the logical specifications of the system are converted to descriptions of the system in terms of real hardware and software. This is a very technical stage and a simple ''overview'' is presented here.
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