RequirementsEngineering

RequirementsEngineering - Foundations of Software...

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Foundations of Software Engineering (for non-software engineers) Requirements Engineering Guy-Vincent Jourdan
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Requirements engineering The requirements are the descriptions of the services provided by the system and its operational constraints. The process of finding out, analyzing, documenting and verifying these services and constraints is called requirement engineering . It is the first phase of the project. Its aim is to create the requirement specification document.
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Requirements engineering Sommerville, I. Software Engineering , Addison-Wesley, 2004 Christensen, M.J. and Thayer, R.H. Project Manager’s Guide to Software Engineering’s Best Practices , IEEE Press, 2002 Van Vliet, H. Software Engineering: Principles and Practice , Wiley, 2000 IEEE 830-1998 Recommended Practice for Software Requirements Specifications IEEE 1233-1998 Guide for Developing System Requirements Specifications
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Requirements engineering The requirements concern not only the functionalities of the system to build, but also other aspects such as performance, cost, hardware etc. Requirements do not specify how the system is going to be designed, but include what is going to be designed. This phase is sometimes called “ requirements analysis ”. However, this phase is really an active one, iterative, co- operative and complex.
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Requirements engineering Requirements engineering is a crucial part of the project, since everything else will come from it. Relative cost of correcting errors: Requirements: 0.1 - 0.2 Design: 0.5 Coding: 1 Unit test: 2 Acceptance test: 5 Maintenance: 20 ( A. Davis, Software Requirements Analysis and Specification , Prentice Hall, 1990 )
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Requirements engineering Even if you don’t take these numbers at face value, it is certainly not surprising that the earlier an error is uncovered, the cheaper it is to fix it. It is thus very important to invest in the requirement engineering phase: if you spend 5% of your budget in the requirement engineering phase, that is one twentieth of the budget. Since everything flows from that phase, it means that every dollars spent there impacts 19$ down the road.
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Defining requirements In order to be useful, the requirements must be defined following some rules. One common shortcoming is vagueness, in the intent ( the application should be user friendly ), or in the goal ( application should be fast ). The IEEE Standard 830-1998 identifies some properties that requirement must have individually , and some properties that they must have collectively. (following slides give an overview)
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Individual requirement properties Requirement must be necessary Ask if that particular requirement is truly needed, useful, is it adding anything? You must be able to state why this requirement is necessary. Requirement must be unambiguous
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This note was uploaded on 01/09/2012 for the course EMP EMP5117 taught by Professor Bohehm during the Fall '11 term at University of Ottawa.

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RequirementsEngineering - Foundations of Software...

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