Definitions[ edit ] Verification and validation are not the same thing, although they are often confused. Boehm succinctly expressed the difference as  Validation: Are we building the right product? Are we building the product right? Building the right product implies creating a Requirements Specification that contains the needs and goals of the stakeholders of the software product. If such artifact is incomplete or wrong, the developers will not be able to build the product the stakeholders want.
This is a form of "artifact or specification validation". Building the product right implies the use of the Requirements Specification as input for the next phase of the development process, the design process, the output of which is the Design Specification.
Then, it also implies the use of the Design Specification to feed the construction process. Every time the output of a process correctly implements its input specification, the software product is one step closer to final verification. If the output of a process is incorrect, the developers are not building the product the stakeholders want correctly.
This kind of verification is called "artifact or specification verification". Software validation[ edit ] Software validation checks that the software product satisfies or fits the intended use high-level checking , i. There are two ways to perform software validation: During internal software validation it is assumed that the goals of the stakeholders were correctly understood and that they were expressed in the requirement artifacts precise and comprehensively.
If the software meets the requirement specification, it has been internally validated. External validation happens when it is performed by asking the stakeholders if the software meets their needs. Different software development methodologies call for different levels of user and stakeholder involvement and feedback; so, external validation can be a discrete or a continuous event.
Successful final external validation occurs when all the stakeholders accept the software product and express that it satisfies their needs. Such final external validation requires the use of an acceptance test which is a dynamic test. However, it is also possible to perform internal static tests to find out if it meets the requirements specification but that falls into the scope of static verification because the software is not running. Artifact or specification validation[ edit ] Requirements should be validated before the software product as whole is ready the waterfall development process requires them to be perfectly defined before design starts; but, iterative development processes do not require this to be so and allow their continual improvement.
Examples of artifact validation: User Requirements Specification validation: User requirements as stated in a document called User Requirements Specification are validated by checking if they indeed represent the will and goals of the stakeholders. This can be done by interviewing them and asking them directly static testing or even by releasing prototypes and having the users and stakeholders to assess them dynamic testing. User input gathered by any peripheral such as keyboard, bio-metric sensor, etc.
Software verification[ edit ] It would imply to verify if the specifications are met by running the software but this is not possible e. Only by reviewing its associated artifacts, someone can conclude if the specifications are met. Artifact or specification verification[ edit ] The output of each software development process stage can also be subject to verification when checked against its input specification see the definition by CMMI below.
Examples of artifact verification: Of the design specification against the requirement specification: Do the architectural design, detailed design and database logical model specifications correctly implement the functional and non-functional requirement specifications? Of the construction artifacts against the design specification: Do the source code, user interfaces and database physical model correctly implement the design specification?
The process of evaluating software during or at the end of the development process to determine whether it satisfies specified requirements. The process of evaluating software to determine whether the products of a given development phase satisfy the conditions imposed at the start of that phase.
Verification, from CMMI's point of view, is evidently of the artifact kind. Software verification ensures that "you built it right" and confirms that the product, as provided, fulfills the plans of the developers.
Software validation ensures that "you built the right thing" and confirms that the product, as provided, fulfills the intended use and goals of the stakeholders. This article has used the strict or narrow definition of verification. Fault — wrong or missing function in the code. Failure — the manifestation of a fault during execution.
The software was not effective. It does not do "what" it is supposed to do. Malfunction — according to its specification the system does not meet its specified functionality. It does not do something "how" it is supposed to do it. Related concepts[ edit ] Both verification and validation are related to the concepts of quality and of software quality assurance. By themselves, verification and validation do not guarantee software quality; planning, traceability , configuration management and other aspects of software engineering are required.
This stands in contrast to software validation. Classification of methods[ edit ] In mission-critical software systems, where flawless performance is absolutely necessary, formal methods may be used to ensure the correct operation of a system. Test case A test case is a tool used in the process. Test cases may be prepared for software verification and software validation to determine if the product was built according to the requirements of the user.
Other methods, such as reviews, may be used early in the life cycle to provide for software validation. ISVV is targeted at safety-critical software systems and aims to increase the quality of software products, thereby reducing risks and costs through the operational life of the software. ISVV provides assurance that software performs to the specified level of confidence and within its designed parameters and defined requirements.
ISVV activities are performed by independent engineering teams, not involved in the software development process, to assess the processes and the resulting products. The ISVV team independency is performed at three different levels: While the latter aim to ensure that the software performs well against the nominal requirements, ISVV is focused on non-functional requirements such as robustness and reliability, and on conditions that can lead the software to fail.
ISVV results and findings are fed back to the development teams for correction and improvement. SoftWcare SL E  , etc. This guide covers the methodologies applicable to all the software engineering phases in what concerns ISVV. ISVV Methodology[ edit ] ISVV is usually composed by five principal phases, these phases can be executed sequentially or as results of a tailoring process.