The advent of new technologies of code reuse and code generation technique also cast doubt on this simple method. Function point metric is a method of measuring the functionality of a proposed software development based upon a count of inputs, outputs, master files, inquires, and interfaces.
The method can be used to estimate the size of a software system as soon as these functions can be identified. It is a measure of the functional complexity of the program. It measures the functionality delivered to the user and is independent of the programming language. It is used primarily for business systems; it is not proven in scientific or real-time applications. Complexity is directly related to software reliability, so representing complexity is important. Complexity-oriented metrics is a method of determining the complexity of a program's control structure, by simplify the code into a graphical representation.
Representative metric is McCabe's Complexity Metric. Test coverage metrics are a way of estimating fault and reliability by performing tests on software products, based on the assumption that software reliability is a function of the portion of software that has been successfully verified or tested. Detailed discussion about various software testing methods can be found in topic Software Testing. Researchers have realized that good management can result in better products.
Research has demonstrated that a relationship exists between the development process and the ability to complete projects on time and within the desired quality objectives. Costs increase when developers use inadequate processes. Higher reliability can be achieved by using better development process, risk management process, configuration management process, etc. Based on the assumption that the quality of the product is a direct function of the process, process metrics can be used to estimate, monitor and improve the reliability and quality of software.
ISO certification, or "quality management standards", is the generic reference for a family of standards developed by the International Standards Organization ISO.
The goal of collecting fault and failure metrics is to be able to determine when the software is approaching failure-free execution. Minimally, both the number of faults found during testing i. Test strategy is highly relative to the effectiveness of fault metrics, because if the testing scenario does not cover the full functionality of the software, the software may pass all tests and yet be prone to failure once delivered.
Usually, failure metrics are based upon customer information regarding failures found after release of the software. The failure data collected is therefore used to calculate failure density, Mean Time Between Failures MTBF or other parameters to measure or predict software reliability. Software Reliability Improvement Techniques Good engineering methods can largely improve software reliability.
Before the deployment of software products, testing, verification and validation are necessary steps. Software testing is heavily used to trigger, locate and remove software defects. Software testing is still in its infant stage; testing is crafted to suit specific needs in various software development projects in an ad-hoc manner. Various analysis tools such as trend analysis, fault-tree analysis, Orthogonal Defect classification and formal methods, etc, can also be used to minimize the possibility of defect occurrence after release and therefore improve software reliability.
After deployment of the software product, field data can be gathered and analyzed to study the behavior of software defects. Software Reliability is a part of software quality. It relates to many areas where software quality is concerned.
The initial quest in software reliability study is based on an analogy of traditional and hardware reliability. Many of the concepts and analytical methods that are used in traditional reliability can be used to assess and improve software reliability too.
Software fault tolerance is a necessary part of a system with high reliability. It is a way of handling unknown and unpredictable software and hardware failures faults [Lyu95] , by providing a set of functionally equivalent software modules developed by diverse and independent production teams. The assumption is the design diversity of software, which itself is difficult to achieve. Software testing serves as a way to measure and improve software reliability.
It plays an important role in the design, implementation, validation and release phases. It is not a mature field. Advance in this field will have great impact on software industry. As software permeates to every corner of our daily life, software related problems and the quality of software products can cause serious problems, such as the Therac accident. The defects in software are significantly different than those in hardware and other components of the system: they are usually design defects, and a lot of them are related to problems in specification.
The unfeasibility of completely testing a software module complicates the problem because bug-free software can not be guaranteed for a moderately complex piece of software. No matter how hard we try, defect-free software product can not be achieved.
Losses caused by software defects causes more and more social and legal concerns. Guaranteeing no known bugs is certainly not a good-enough approach to the problem. Software reliability is a key part in software quality. The study of software reliability can be categorized into three parts: modeling, measurement and improvement. Software reliability modeling has matured to the point that meaningful results can be obtained by applying suitable models to the problem.
There are many models exist, but no single model can capture a necessary amount of the software characteristics. Assumptions and abstractions must be made to simplify the problem. There is no single model that is universal to all the situations. Software reliability measurement is naive.
Measurement is far from commonplace in software, as in other engineering field. Software reliability can not be directly measured, so other related factors are measured to estimate software reliability and compare it among products. Development process, faults and failures found are all factors related to software reliability. Software reliability improvement is hard. The difficulty of the problem stems from insufficient understanding of software reliability and in general, the characteristics of software.
Until now there is no good way to conquer the complexity problem of software. Complete testing of a moderately complex software module is infeasible. Defect-free software product can not be assured. Realistic constraints of time and budget severely limits the effort put into software reliability improvement. As more and more software is creeping into embedded systems, we must make sure they don't embed disasters.
If not considered carefully, software reliability can be the reliability bottleneck of the whole system. Ensuring software reliability is no easy task.
As hard as the problem is, promising progresses are still being made toward more reliable software. Related questions. Giving reasons for your answer, suggest which dependability attributes are likely to be most critical for the following systems Duplicate: Using an example, explain why it is important when developing dependable systems to consider these as sociotechnical systems and not simply as technical software and hardware systems.
Using an example, explain why it is important when developing dependable systems to consider these as sociotechnical systems and not simply as technical software and hardware systems. Why is system integration a particularly critical part of the systems development process? Suggest three sociotechnical issues that may cause difficulties in the system integration process. Reliability and safety are related but distinct dependability attributes.
Describe the most important distinction between these attributes and explain why it is possible for a reliable system to be unsafe and vice versa. Suggest the most appropriate generic software process model for managing the development of a university accounting system to replace an existing manual system giving reasons.
Giving reasons for your answer based on the type of system being developed, suggest the most appropriate generic software process model that might be used to develop a system that automatically controls the speed of a motor vehicle cruise control. Explain why incremental development is the most effective approach for developing business software systems. Why is this model less appropriate for real-time systems engineering?
Explain why adaptors are usually needed when systems are constructed by integrating COTS products. Suggest three practical problems that might arise in writing adaptor software to link two COTS application products.
Explain why adaptors are usually needed when systems are constructed by integrating application systems. Suggest three practical problems that might arise in writing adaptor software to link two application systems. Duplicate: What is the most important difference between generic software product development and custom software development? What might this mean in practice for users of generic software products? Suggest appropriate reliability metrics for the classes of software system below.
Give reasons for your choice of metric. Predict the usage of these systems and suggest appropriate values for the reliability metrics. Explain why legacy systems should be thought of as sociotechnical systems rather than simply software systems that were developed using old technology. From Figure 9. Using a diagram, suggest what activities might be involved in change. It is used to identify the functionality, which is obligatory for the software to behold in it.
It is used to cover the non —functional areas like the appearance of the software, performance validation, compatibility, integrating ability, load passed through the software in real-time, etc. In the Design and coding stages, the evaluation for the software reliability is performed on the action plan. The areas on which the estimation is applied are the size of the software, the usability aspects, and the component of the software.
It is important to keep the system in smaller units so that the possibility for mishaps is reduced in a highly remarkable way. When the fault occurrences are contained, then the reliability scale will perform as required for the analysis.
Instead of having one big complex system, it is a good practice to have multiple components with understandable and easily operable units of the software. During the testing phase, the reliability metrics used are made up of two different segments. And, the other segment is to evaluate the program functions and its performance. The first one is considered to be a black box testing process, and the later is known to be a white box testing typically performed by the developer.
The testing process is carried out against the already placed documentations, in the name of requirement specifications from the client. So, any mismatch in this stage will be reported and handled as the part of the bug fix and tracked in the form of a defect life cycle.
It is used to achieve an effective way of validating the entire system and to make sure that every nook and corner of the developed system is validated.
The below are the methods used, based on the required type of metric analysis, during the above-mentioned software development phases,.
As the name says, the Prediction Model is built based on the assumptions that one has on the requirements provided for developing the given software application.
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