A number of key issues must be dealt with to ensure the effective maintenance of software. Software maintenance provides unique technical and management challenges for software engineers—for example, trying to find a fault in software containing a large number of lines of code that another software engineer developed. Similarly, competing with software developers for resources is a constant battle. Planning for a future release, which often includes coding the next release while sending out emergency patches for the current release, also creates a challenge. The following section presents some of the technical and management issues related to software maintenance. They have been grouped under the following topic headings:
• technical issues,
• management issues,
• cost estimation, and
• measurement.
Technical Issues
Limited Understanding
Limited understanding refers to how quickly a software engineer can understand where to make a change or correction in software that he or she did not develop. Research indicates that about half of the total maintenance effort is devoted to understanding the software to be modified. Thus, the topic of software comprehension is of great interest to software engineers. Comprehension is more difficult in text-oriented representation—in source code, for example—where it is often difficult to trace the evolution of software through its releases/ versions if changes are not documented and if the developers are not available to explain it, which is often the case. Thus, software engineers may initially have a limited understanding of the software; much has to be done to remedy this.
Testing
The cost of repeating full testing on a major piece of software is significant in terms of time and money. In order to ensure that the requested problem reports are valid, the maintainer should replicate or verify problems by running the appropriate tests. Regression testing (the selective retesting of software or a component to verify that the modifications have not caused unintended effects) is an important testing concept in maintenance. Additionally, finding time to test is often difficult. Coordinating tests when different members of the maintenance team are working on different problems at the same time remains a challenge. When software performs critical functions, it may be difficult to bring it offline to test. Tests cannot be executed in the most meaningful place–the production system.
Impact Analysis
Impact analysis describes how to conduct, costeffectively, a complete analysis of the impact of a change in existing software. Maintainers must possess an intimate knowledge of the software’s structure and content. They use that knowledge to perform impact analysis, which identifies all systems and software products affected by a software change request and develops an estimate of the resources needed to accomplish the change. Additionally, the risk of making the change is determined. The change request, sometimes called a modification request (MR) and often called a problem report (PR), must first be analyzed and translated into software terms. Impact analysis is performed after a change request enters the software configuration management process. IEEE 14764 states the impact analysis tasks:
• analyze MRs/PRs;
• replicate or verify the problem;
• develop options for implementing the modification;
• document the MR/PR, the results, and the execution options;
• obtain approval for the selected modification option.
The severity of a problem is often used to decide how and when it will be fixed. The software engineer then identifies the affected components. Several potential solutions are provided, followed by a recommendation as to the best course of action. Software designed with maintainability in mind greatly facilitates impact analysis.
Maintainability
IEEE 14764 defines maintainability as the capability of the software product to be modified. Modifications may include corrections, improvements, or adaptation of the software to changes in environment as well as changes in requirements and functional specifications.
As a primary software quality characteristic, maintainability should be specified, reviewed, and controlled during software development activities in order to reduce maintenance costs. When done successfully, the software’s maintainability will improve. Maintainability is often difficult to achieve because the subcharacteristics are often not an important focus during the process of software development. The developers are, typically, more preoccupied with many other activities and frequently prone to disregard the maintainer’s requirements. This in turn can, and often does, result in a lack of software documentation and test environments, which is a leading cause of difficulties in program comprehension and subsequent impact analysis. The presence of systematic and mature processes, techniques, and tools helps to enhance the maintainability of software.
Management Issues
Alignment with Organizational Objectives
Organizational objectives describe how to demonstrate the return on investment of software maintenance activities. Initial software development is usually project-based, with a defined time scale and budget. The main emphasis is to deliver a product that meets user needs on time and within budget. In contrast, software maintenance often has the objective of extending the life of software for as long as possible. In addition, it may be driven by the need to meet user demand for software updates and enhancements. In both cases, the return on investment is much less clear, so that the view at the senior management level is often that of a major activity consuming significant resources with no clear quantifiable benefit for the organization.
Staffing
Staffing refers to how to attract and keep software maintenance staff. Maintenance is not often viewed as glamorous work. As a result, software maintenance personnel are frequently viewed as “second-class citizens,” and morale therefore suffers.
Process
The software life cycle process is a set of activities, methods, practices, and transformations that people use to develop and maintain software and its associated products. At the process level, software maintenance activities share much in common with software development (for example, software configuration management is a crucial activity in both). Maintenance also requires several activities that are not found in software development (see section 3.2 on unique activities for details). These activities present challenges to management.
Organizational Aspects of Maintenance
Organizational aspects describe how to identify which organization and/or function will be responsible for the maintenance of software. The team that develops the software is not necessarily assigned to maintain the software once it is operational. In deciding where the software maintenance function will be located, software engineering organizations may, for example, stay with the original developer or go to a permanent maintenance-specific team (or maintainer). Having a permanent maintenance team has many benefits:
• allows for specialization;
• creates communication channels;
• promotes an egoless, collegiate atmosphere;
• reduces dependency on individuals;
• allows for periodic audit checks.
Since there are many pros and cons to each option, the decision should be made on a case-bycase basis. What is important is the delegation or assignment of the maintenance responsibility to a single group or person, regardless of the organization’s structure.
Outsourcing
Outsourcing and offshoring software maintenance has become a major industry. Organizations are outsourcing entire portfolios of software, including software maintenance. More often, the outsourcing option is selected for less mission-critical software, as organizations are unwilling to lose control of the software used in their core business. One of the major challenges for outsourcers is to determine the scope of the maintenance services required, the terms of a service-level agreement, and the contractual details. Outsourcers will need to invest in a maintenance infrastructure, and the help desk at the remote site should be staffed with native-language speakers. Outsourcing requires a significant initial investment and the setup of a maintenance process that will require automation.
Maintenance Cost Estimation
Software engineers must understand the different categories of software maintenance, discussed above, in order to address the question of estimating the cost of software maintenance. For planning purposes, cost estimation is an important aspect of planning for software maintenance.
Cost Estimation
Maintenance cost estimates are affected by many technical and nontechnical factors. IEEE 14764 states that “the two most popular approaches to estimating resources for software maintenance are the use of parametric models and the use of experience” . A combination of these two can also be used.
Parametric Models
Parametric cost modeling (mathematical models) has been applied to software maintenance. Of significance is that historical data from past maintenance are needed in order to use and calibrate the mathematical models. Cost driver attributes affect the estimates.
Experience
Experience, in the form of expert judgment, is often used to estimate maintenance effort. Clearly, the best approach to maintenance estimation is to combine historical data and experience. The cost to conduct a modification (in terms of number of people and amount of time) is then derived. Maintenance estimation historical data should be provided as a result of a measurement program
Software Maintenance Measurement
Entities related to software maintenance, whose attributes can be subjected to measurement, include process, resource, and product . There are several software measures that can be derived from the attributes of the software, the maintenance process, and personnel, including size, complexity, quality, understandability, maintainability, and effort. Complexity measures of software can also be obtained using available commercial tools. These measures constitute a good starting point for the maintainer’s measurement program
Specific Measures
The maintainer must determine which measures are appropriate for a specific organization based on that organization’s own context. The software quality model suggests measures that are specific for software maintenance. Measures for subcharacteristics of maintainability include the following
• Analyzability: measures of the maintainer’s effort or resources expended in trying either to diagnose deficiencies or causes of failure or to identify parts to be modified.
• Changeability: measures of the maintainer’s effort associated with implementing a specified modification.
• Stability: measures of the unexpected behavior of software, including that encountered during testing.
• Testability: measures of the maintainer’s and users’ effort in trying to test the modified software. • Other measures that maintainers use include
• size of the software,
• complexity of the software ,
• understandability, and
• maintainability.
Providing software maintenance effort, by categories, for different applications provides business information to users and their organizations. It can also enable the comparison of software maintenance profiles internally within an organization.
Back - 1 - Fundamentals
Next - 3 - Maintenance Process
Home - Software Maintenance
Main - The BOK
Published on : 30-May-2018
Ref no : DTC-WPUB-000037
About Author
Comments
Post a Comment