Tuesday, April 21, 2009

Verification and Validation (V & V)

In software project management, software testing, and software engineering, Verification and Validation (V&V) is the process of checking that a software system meets specifications and that it fulfils its intended purpose. It is normally part of the software testing process of a project.


It is also known as software quality control.
Validation checks that the product design satisfies or fits the intended usage (high-level checking) — i.e., you built the right product. This is done through dynamic testing and other forms of review.
According to the Capability Maturity Model (CMMI-SW v1.1), “Validation - The process of evaluating software during or at the end of the development process to determine whether it satisfies specified requirements. [IEEE-STD-610] Verification- 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. [IEEE-STD-610]."

In other words, validation ensures that the product actually meets the user's needs, and that the specifications were correct in the first place, while verification is ensuring that the product has been built according to the requirements and design specifications. Validation ensures that ‘you built the right thing’. Verification ensures that ‘you built it right’. Validation confirms that the product, as provided, will fulfill its intended use.

Validation and Verification
Verification is one aspect of testing a product's fitness for purpose. Validation is the complementary aspect. Often one refers to the overall checking process as V & V.

* Validation: "Are we trying to make the right thing?", i.e., does the product do what the user really requires?
Have we built the right software (i.e., is this what the customer wants?)?
It is product based.

* Verification: "Have we made what we were trying to make?", i.e., does the product conform to the specifications?
Have we built the software right (i.e., does it match the specification?)?
It is process based.

The verification process consists of static and dynamic parts. E.g., for a software product one can inspect the source code (static) and run against specific test cases (dynamic). Validation usually can only be done dynamically, i.e., the product is tested by putting it through typical usages and atypical usages ("Can we break it?").

Within the modeling and simulation community, the definitions of validation, verification and accreditation are similar:

* Validation: The process of determining the degree to which a model, simulation, or federation of models and simulations, and their associated data are accurate representations of the real world from the perspective of the intended use(s).
* Accreditation is the formal certification that a model or simulation is acceptable to be used for a specific purpose.
* Verification: The process of determining that a computer model, simulation, or federation of models and simulations implementations and their associated data accurately represents the developer's conceptual description and specifications.

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.

Classification of methods

In mission-critical systems where flawless performance is absolutely necessary, formal methods can be used to ensure the correct operation of a system. However, often for non-mission-critical systems, formal methods prove to be very costly and an alternative method of V&V must be sought out. In this case, syntactic methods are often used.

Test cases
A test case is a tool used in the V&V process.

The QA team prepares test cases for verification--to determine if the process that was followed to develop the final product is right.

The QC team uses a test case for validation--if the product is built according to the requirements of the user. Other methods, such as reviews, when used early in the Software Development Life Cycle provide for validation.

Independent Verification and Validation

Verification and validation often is carried out by a separate group from the development team; in this case, the process is called "Independent Verification and Validation", or IV&V.

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