Errors in the specification of information systems are much easier and less costly to correct when the specifications are created than after the system has been implemented. However, specifications are usually not subject to rigorous testing of the kind that is applied to the complete system mainly because the lack of formalization and the work required to analyze them. The formal approach was used for defining and operationalizing notions of completeness and consistency of specifications. Testing the specifications for lack of completeness and consistency can help the analyst in identifying potential specification errors. Experimental computerized specification analysis tools were developed for detecting potential specification problems and their possible sources.
Decomposition is the breakdown of a complex system into smaller, relatively independent, units.
Decomposition is the primary tool available to simplify the construction of complex man-made systems and is an essential part of systems analysis and design. However, there is no general approach for accomplishing it and it usually relies on an analyst's experience and expertise. A method for system decomposition was developed based on a formal specification scheme, formal definition of good decomposition, heuristic rules, and a measure of complexity. The method has been implemented as a set of experimental computerized tools, and applied to a standard problem for which other designs already existed. A major difficulty in the process of information systems analysis and design is that users describe the application in informal terms and the systems analyst needs to convert this knowledge into technical specifications.