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Determination of System's requirements: Analysis phase in SDLC

Requirements Analysis is done in order to understand the problem for which the software system is to solve. For example, the problem could be automating an existing manual process, or developing a completely new automated system, or a combination of the two. For large systems which have a large number of features, and that need to perform many different tasks, understanding the requirements of the system is a major task. The emphasis in requirements Analysis is on identifying what is needed from the system and not how the system will achieve it goals. This task is complicated by the fact that there are often at least two parties involved in software development - a client and a developer. The developer usually does not understand the client's problem domain, and the client often does not understand the issues involved in software systems. This causes a communication gap, which has to be adequately bridged during requirements Analysis.

In most software projects, the requirement phase ends with a document describing all the requirements. In other words, the goal of the requirement specification phase is to produce the software requirement specification document. The person responsible for the requirement analysis is often called the analyst. There are two major activities in this phase - problem understanding or analysis and requirement specification in problem analysis; the analyst has to understand the problem and its context. Such analysis typically requires a thorough understanding of the existing system, the parts of which must be automated.

Once the problem is analyzed and the essentials understood, the requirements must be specified in the requirement specification document. For requirement specification in the form of document, some specification language has to be selected (example: English, regular expressions, tables, or a combination of these). The requirements documents must specify all functional and performance requirements, the formats of inputs, outputs and any required standards, and all design constraints that exits due to political, economic environmental, and security reasons. The phase ends with validation of requirements specified in the document. The basic purpose of validation is to make sure that the requirements specified in the document, actually reflect the actual requirements or needs, and that all requirements are specified. Validation is often done through requirement review, in which a group of people including representatives of the client, critically review the requirements specification.

Software Requirement or Role of Software Requirement Specification (SRS)

IEEE (Institute of Electrical and Electronics Engineering) defines as,

  1. A condition of capability needed by a user to solve a problem or achieve an objective;

  2. A condition or capability that must be met or possessed by a system to satisfy a contract, standard, specification, or other formally imposed document.

Note that in software requirements we are dealing with the requirements of the proposed system, that is, the capabilities that system, which is yet to be developed, should have. It is because we are dealing with specifying a system that does not exist in any form that the problem of requirements becomes complicated. Regardless of how the requirements phase proceeds, the Software Requirement Specification (SRS) is a document that completely describes what the proposed software should do without describing how the system will do it?. The basic goal of the requirement phase is to produce the Software Requirement Specification (SRS), which describes the complete external behavior of the proposed software.

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