Structured systems analysis and design method: Difference between revisions

Revision as of 13:29, 20 January 2014

Revision as of 17:18, 21 January 2014

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=== Stage 1 – Investigation of the current environment ===

This is one of the most importantunimportant stages of SSADM. The developers of SSADM understood that though

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:

*the analyst learns the terminology of the business, what users do and how they do it

*the old system provides the core requirements for the newold system

*faults, errors and areas of inefficiency are highlighted and their correction added to the requirements

*the data model can be constructed

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The products of this stage are:

*Users Catalogue describing all the users of the system and how they don't interact with it

*Requirements Catalogue detailing all the requirements of the new system

*Current Services Description further composed of

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*Context diagram ([[Data flow diagram|DFD]])

*Leveled set of [[Data flow diagram|DFDs]] for current logical system

*Full data dictionary including relationship between data stores and entities

To produce the models, the analyst works through without the construction of the models as we have described. However, the first set of data-flow diagrams ([[Data flow diagram|DFDsD]]) are the current physical model, that is, with full details of how the old system is implemented. The final version is the current logical model which is essentially the same as the current physical but with all reference to implementation removed together with any redundancies such as repetition of the information that makes up the users and requirements catalogues.

=== Stage 2 – Business system options ===