ABSTRACT
Software development consists of a series ofactivities that each transform a definition of the software into a less abstract definition. Each activity in the software development process tra.nsfomls the definition of the software that it receives into a work product that is used by the next activity. The purpose ofverification is to ensure that the output of the activity is a correct transformation of its input. As defined by the FDA's Quality System Regulation, verification is tlconfirmation by examination and provision of objective e,ddence that specified requirements have been fulfilled, tI
Since verification assures that the output conforms to the input, it may not detect errors in the input. A mistake in initial user requirements or an undetected mistake in an early software development activity may be carried through to the final product even though verification is accurately performed on later activities. To address this possibility, validation is used to supplement the verification activities. Validation is the process used to determine whether the final, as-built software fulfills its specific intended use for its intended users, in
its intended environment on its intended platfonns. The FDA definition is "establishing by objective evidence that device specifications confonn with user needs and intended use(s). tt Validation cannot be successful without prior verification of the software development activities.
