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International Organization for Standardization (ISO)/IEC 12207The SEI is not the only quality or standards organization concerned with software processes and life cycles. As early as 1989, it was recognized that the standard imposed upon defense and other government contractors, Department of Defense Standard (DOD STD) 2167A, was not well suited to use with projects employing object-oriented design (OOD) or Rapid Application Development (RAD) methods. A new Military Standard (MIL STD) 498 was intended to correct issues with these methods, and it does indeed solve some of the problems. A third approach, International Organization for Standardization (ISO)/IEC 12207, which developed independently from MIL STD 498, is another step forward. It describes the major component processes of a complete software life cycle, their interfaces with one another, and the high-level relations that govern their interactions. As shown in Figure 4-7, ISO/IEC 12207 lists 12 engineering activities, following process implementation, that are similar to the phases in a typical SLCM:
Figure 4-7. Engineering View of ISO/IEC 12207The ISO/IEC 12207 approach has been described as an implementation of a Plan-Do-Check-Act (PDCA) cycle, discussed in Chapter 3, "Process Overview." The intent is that the engineer should check the output of an engineering task before it becomes input to the next task. "The activities of the ISO/IEC 12207 development process have independence from one another … they are not ordered in a waterfall sequence and, … there are no requirements in the international standard that dictate which of them must be executed first and which next." In fact, ISO/IEC 12207 says explicitly, in paragraph 5.3.1.1, that "these activities and tasks may overlap or interact and may be performed iteratively or recursively." Paragraph 1.5 states that "this international standard does not prescribe a specific life cycle model or software development method." Paragraph 5.3.1.1 states that, unless the contract stipulates one, "the developer shall define or select a software life cycle model appropriate to the scope, magnitude, and complexity of the project. The activities and tasks of the development process shall be selected and mapped onto the life cycle model." The intent and effect of the language in the international standard are to provide flexibility in ordering activities, and to choose development models to avoid the waterfall bias of other standards.[8] Individuals and organizations respected in the software, project management, and quality arenas are in agreement on the necessity of process and life cycle process, in particular. PMI, Boehm, IT-Systems of the Federal Republic of Germany, the SEI, and the ISO have all recommended having a software development life cycle, one that is carefully selected and tailored for project suitability. |
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