Ontological Concepts of Non-Functional Requirements Applied to Particular Situations in Measurement and Evaluation Projects

Abstract

The terms Functional Requirement and Non-Functional Requirement (NFR) are intertwined concepts but aim at different purposes. In a nutshell, functional requirements state what an entity must do by referring to its features and capabilities (functions), while non-functional requirements state quality aspects that this entity must achieve. The present paper discusses the main terms and relationships for the Non-Functional Requirements (NFRs) domain ontology, which is located at the top-domain level in the context of a five-tier ontological architecture for specifying knowledge. In this ontological context, the term NFR does not represent a concrete entity (particular thing), but rather a quality-, constraint-related human assertion of a certain aspect of the entity to be measured and evaluated. Also, an NFR as an assertion can deal with an entity category (thing category) as a universal abstraction. As a consequence, the quality aspect attributed, for example, to a particular entity –both as a class and its individuals– can refer to its parts, such as the properties and/or capabilities (powers) of the entity, or the entity as a whole. To better understand the terms and relationships of the NFRs ontology, some grounding in the semantics of the foundational concepts such as Thing, Thing Category, and Assertion is needed. Ultimately, to validate the applicability of the ontological conceptualization of NFRs, three practical cases carried out in particular situations of measurement and evaluation projects are discussed, and the benefits of this ontological proposal are also highlighted.