Software Engineering-Requirements Analysis


Requirements analysis is a software engineering task that bridges the gap between system level requirements engineering and software design . Requirements engineering activities result in the specification of software’s operational characteristics (function, data, and behavior), indicate software's interface with other system elements, and establish constraints that software must meet. Requirements
analysis allows the software engineer (sometimes called analyst in this role) to refine the software allocation and build models of the data, functional, and behavioral domains that will be treated by software. Requirements analysis provides the software designer with a representation of information, function, and behavior that can be translated to data, architectural, interface, and component-level designs. Finally,the requirements specification provides the developer and the customer with the means to assess quality once software is built.

Software requirements analysis may be divided into five areas of effort: (1) problem recognition, (2) evaluation and synthesis, (3) modeling, (4) specification, and (5) review. Initially, the analyst studies the System Specification (if one exists) and the Software Project Plan. It is important to understand software in a system context and to review the software scope that was used to generate planning estimates. Next, communication for analysis must be established so that problem recognition is ensured. The goal is recognition of the basic problem elements as perceived by the customer/users.


Problem evaluation and solution synthesis is the next major area of effort for analysis. The analyst must define all externally observable data objects, evaluate the flow and content of information, define and elaborate all software functions, understand software behavior in the context of events that affect the system, establish system interface characteristics, and uncover additional design constraints. Each of these tasks serves to describe the problem so that an overall approach or solution may be synthesized.

For example, an inventory control system is required for a major supplier of auto parts. The analyst finds that problems with the current manual system include (1) inability to obtain the status of a component rapidly, (2) two- or three-day turnaround to update a card file, (3) multiple reorders to the same vendor because there is no way to associate vendors with components, and so forth. Once problems have been identified, the analyst determines what information is to be produced by the new system and what data will be provided to the system. For instance, the customer desires a daily report that indicates what parts have been taken from inventory and how many similar parts remain. The customer indicates that inventory  clerks will log the identification number of each part as it leaves the inventory area.

Upon evaluating current problems and desired information (input and output), the analyst begins to synthesize one or more solutions. To begin, the data objects, processing functions, and behavior of the system are defined in detail. Once this information has been established, basic architectures for implementation are considered. A client/server approach would seem to be appropriate, but does the software to support this architecture fall within the scope outlined in the Software Plan? A database management system would seem to be required, but is the user/customer's need for associativity justified? The process of evaluation and synthesis continues until both analyst and customer feel confident that software can be adequately specified for subsequent development steps.

Throughout evaluation and solution synthesis, the analyst's primary focus is on "what," not "how." What data does the system produce and consume, what functions must the system perform, what behaviors does the system exhibit, what interfaces are defined and what constraints apply? During the evaluation and solution synthesis activity, the analyst creates models of the system in an effort to better understand data and control flow, functional processing, operational behavior, and information content. The model serves as a foundation for software design and as the basis for the creation of specifications for the software.
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