Software Requirements Engineering Computer Software Technology Has

Software Requirements Engineering Computer software technology has improved significantly over the past decade leading to more efficient and comprehensive information systems. With the innumerable computing systems there is also a corresponding increase in the complexity of these systems. Today software requirements analysis has become an indispensable part of software development. Over the years there has been a continued stress on the importance of a properly planned project evaluation, requirement specification and designing.

The system development life cycle incorporates the complete analysis, design and maintenance of any software project wherein each phase of the project is meticulously planned and based on the previous phase. Let us consider the requirements engineering process in a little detail. The software requirements engineering process is part of the analysis phase of the software development life cycle. Once the requirements are thoroughly assessed a comprehensive software requirements specification is drafted. This is a technical specification of the software requirements.

Unlike the software-designing phase, which deals with the actual technicalities of implementing the software, the requirements phase just specifies what is expected of the software product. A properly developed specification is a prerequisite for the success of the software product. One of the main causes for the failure of software projects is the poor attention paid to requirements engineering. Poorly drafted requirements specification may lead to developing software that doesn't satisfy the needs of the user.

The Software Requirements Specification The software requirements specification is a comprehensive document, which presents all the different aspects involved in the software development. This includes the product overview, data flow, functional requirements, performance requirements, methods to handle exceptions, provisions for modification etc. It is desirable that the software specification or requirements report should be correct, complete, consistent, clear, functional, verifiable, traceable and easily changeable. If the requirements are badly stated or incomplete we might end up developing software that satisfies the requirements but still way behind the user expectations.

[Fairley, 93] There are many models that are used in the software development life cycle. All of these models invariably generate a 'requirements specification' document as the basis of the development. The very first phase in SDLC is developing the feasibility report. The scope of the proposed project is precisely identified and the discrepancies in the current (existing) system are ascertained. Once the preliminary investigation is over and the project is found to be technically, economically and operationally feasible the next step is the requirements analysis.

After understanding the system the next phase is to detail the operations to be performed by the system, in context of the objects both external and internal to the system. The inputs and outputs to the system as well as the data to be retained by the system are identified. Several control features that can be used by the user to monitor the system are specified. This detailed analysis is documented in a report form called as the 'Functional Specification'.

Once the analysis part is over the developers have a clear understanding as to the 'what is to be done'. The developers proceed with the system design based on the report of the 'Functional Specification'. The programmers use the design specification for developing the software. At this stage the actual coding of the program is done. Documentation of the program is done simultaneously as it very indispensable for testing as well as maintenance of the program in future.

The software thus developed is tested with test data to check for possible errors in logic before the actual implementation process. Elicitation, solution determination, specification and maintenance are the different aspects of requirements engineering. Languages for Requirements specification (Automated tools) For real time software systems such as defense applications requirements specification is of utmost importance. The latest automated tools must be used in conjunction with the manual systems to arrive at a proper requirement specification.

Furthermore, a particular functional specification can be satisfied by any one of the different software structures available and hence in deciding upon a particular structure we have to look into quality aspect. The software architecture that is chosen is critical in some applications, especially the real-time defense applications. Rick Kazman of SEI Interactive explains. "Each requirement suggests certain architectural structures and rules other ones out.

I will choose one set of architectural structures over another because I know that it's a good architecture for being able to predict and control end-to-end latency or throughput, or that it's a good architecture for high availability." [Thomas] PSL/PSA Currently we have a lot of special tools, which are designed to automate the analysis process of requirement specifications. (The PSL (Problem Statement Language) and the PSA (problem Statement Analyzer)).

This tool treats the whole system as a set of objects and assists in generating a requirements specification report by establishing relationships between the different objects of the system. The inputs, outputs, data structure, data derivation, System size and volume, System Properties and project management are some of the major aspects of the PSL. The requirements stated in the PSL are automatically analyzed by the PSA. The PSl/PSA tool is currently finding application in air defense systems and in data processing applications.

RSL/REVS The RSL (Requirements Statement Language) was especially designed for real-time systems to produce concise requirement specifications. RSL uses the flow-oriented approach. RSL employs a variety of different types of predefined element types, relationships, attributes and structures. The flow-oriented approach involves a stimulus -response method. The RSL has both graphical as well as textual representation of the flows. [Fairley, 117] Structured Analysis and Design Technique Known as the language of structured analysis the SDAT model is a graphical language. The arcs depict the flow of data between the different activities.

(Actigrams). An SDAT model is made up of the SA diagrams. The SDAT helps to have a clear understanding of the requirements because it employs the top down approach. SDAT can be used for any kind of project though it is especially suited for complex systems. Similar to SDAT the SSA (Structured System Analysis) employs a graphical language to build system models. The special quality in SSA is that it incorporates database concepts.

Effect of Bad Requirements analysis The lack of correct requirements specification has proved to the debacle of many a software projects. As a case in point we.