The objective of software maintenance is to modify existing software while preserving its integrity. The international standard also states the importance of having some maintenance activities prior to the final delivery of software (predelivery activities). Notably, IEEE 14764 emphasizes the importance of the predelivery aspects of maintenance—planning, for example.
Nature of Maintenance
Software maintenance sustains the software product throughout its life cycle (from development to operations). Modification requests are logged and tracked, the impact of proposed changes is determined, code and other software artifacts are modified, testing is conducted, and a new version of the software product is released. Also, training and daily support are provided to users. The term maintainer is defined as an organization that performs maintenance activities. In this KA, the term will sometimes refer to individuals who perform those activities, contrasting them with the developers.
IEEE 14764 identifies the primary activities of software maintenance as process implementation, problem and modification analysis, modification implementation, maintenance review/acceptance, migration, and retirement. These activities are discussed in section 3.2, Maintenance Activities.
Maintainers can learn from the developers’ knowledge of the software. Contact with the developers and early involvement by the maintainer helps reduce the overall maintenance effort. In some instances, the initial developer cannot be reached or has moved on to other tasks, which creates an additional challenge for maintainers. Maintenance must take software artifacts from development (for example, code or documentation) and support them immediately, then progressively evolve/maintain them over a software life cycle.
Need for Maintenance
Maintenance is needed to ensure that the software continues to satisfy user requirements. Maintenance is applicable to software that is developed using any software life cycle model (for example, spiral or linear). Software products change due to corrective and non corrective software actions. Maintenance must be performed in order to
• correct faults;
• improve the design;
• implement enhancements;
• interface with other software;
• adapt programs so that different hardware, software, system features, and telecommunications facilities can be used;
• migrate legacy software; and
• retire software.
Five key characteristics comprise the maintainer’s activities:
• maintaining control over the software’s dayto-day functions;
• maintaining control over software modification;
• perfecting existing functions;
• identifying security threats and fixing security vulnerabilities; and
• preventing software performance from degrading to unacceptable levels.
Majority of Maintenance Costs
Maintenance consumes a major share of the financial resources in a software life cycle. A common perception of software maintenance is that it merely fixes faults. However, studies and surveys over the years have indicated that the majority, over 80 percent, of software maintenance is used for noncorrective actions [2*, figure 4.1]. Grouping enhancements and corrections together in management reports contributes to some misconceptions regarding the high cost of corrections. Understanding the categories of software maintenance helps to understand the structure of software maintenance costs. Also, understanding the factors that influence the maintainability of software can help to contain costs. Some environmental factors and their relationship to software maintenance costs include the following:
• Operating environment refers to hardware and software.
• Organizational environment refers to policies, competition, process, product, and personnel.
Evolution of Software
Software maintenance in terms of evolution was first addressed in the late 1960s. Over a period of twenty years, research led to the formulation of eight “Laws of Evolution.” Key findings include a proposal that maintenance is evolutionary development and that maintenance decisions are aided by understanding what happens to software over time. Some state that maintenance is continued development, except that there is an extra input (or constraint)–in other words, existing large software is never complete and continues to evolve; as it evolves, it grows more complex unless some action is taken to reduce this complexity.
Categories of Maintenance
Three categories (types) of maintenance have been defined: corrective, adaptive, and perfective
• Corrective maintenance: reactive modification (or repairs) of a software product performed after delivery to correct discovered problems. Included in this category is emergency maintenance, which is an unscheduled modification performed to temporarily keep a software product operational pending corrective maintenance.
• Adaptive maintenance: modification of a software product performed after delivery to keep a software product usable in a changed or changing environment. For example, the operating system might be upgraded and some changes to the software may be necessary.
• Perfective maintenance: modification of a software product after delivery to provide enhancements for users, improvement of program documentation, and recoding to improve software performance, maintainability, or other software attributes.
• Preventive maintenance: modification of a software product after delivery to detect and correct latent faults in the software product before they become operational faults.
IEEE 14764 classifies adaptive and perfective maintenance as maintenance enhancements. It also groups together the corrective and preventive maintenance categories into a correction category
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Published on : 30-May-2018
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