Non-functional requirements (NFRs) are commonly distinguished from functional requirements by differentiating how the system shall do something in contrast to what the system shall do. This distinction is not only prevalent in research, but also influences how requirements are handled in practice. NFRs are usually documented separately from functional requirements, without quantitative measures, and with relatively vague descriptions. As a result, they remain difficult to analyze and test. Several authors argue, however, that many so-called NFRs actually describe behavioral properties and may be treated the same way as functional requirements. In this paper, we empirically investigate this point of view and aim to increase our understanding on the nature of NFRs addressing system properties. We report on the classification of 530 NFRs extracted from 11 industrial requirements specifications and analyze to which extent these NFRs describe system behavior. Our results suggest that most "non-functional" requirements are not non-functional as they describe behavior of a system. Consequently, we argue that many so-called NFRs can be handled similarly to functional requirements.
NFR classifications. There exist several classification schemes for NFRs in literature (e.g., @cite_23 @cite_2 @cite_17 @cite_18 @cite_7 @cite_30 ). One example for such a classification, which is based on a quality model, is the @cite_17 . It defines external and internal quality of a software system and derives several quality characteristics (e.g., Functionality--Security or Portability--Installability ). Sommerville further provides a classification scheme based on a distinction between process requirements , product requirements , and external requirements @cite_7 . We base our distinction of NFR classes on the classification. Furthermore, we exclude process requirements from our study, as they do not describe properties of the system itself.
@cite_30 @cite_18 @cite_7 @cite_23 @cite_2 @cite_17
2346441090 2143259336 2044631171 2144634407
In this paper, we describe a novel unsupervised approach for detecting, classifying, and tracing non-functional software requirements (NFRs). The proposed approach exploits the textual semantics of software functional requirements (FRs) to infer potential quality constraints enforced in the system. In particular, we conduct a systematic analysis of a series of word similarity methods and clustering techniques to generate semantically cohesive clusters of FR words. These clusters are classified into various categories of NFRs based on their semantic similarity to basic NFR labels. Discovered NFRs are then traced to their implementation in the solution space based on their textual semantic similarity to source code artifacts. Three software systems are used to conduct the experimental analysis in this paper. The results show that methods that exploit massive sources of textual human knowledge are more accurate in capturing and modeling the notion of similarity between FR words in a software system. Results also show that hierarchical clustering algorithms are more capable of generating thematic word clusters than partitioning clustering techniques. In terms of performance, our analysis indicates that the proposed approach can discover, classify, and trace NFRs with accuracy levels that can be adequate for practical applications. Quality characteristics are vital for the success of software systems. To remedy the problems inherent in ad hoc development, a framework has been developed to deal with non-functional requirements (quality requirements or NFRs). Taking the premise that the quality of a product depends on the quality of the process that leads from high-Ievel NFRs to the product, the framework's objectives are to represent NFR-specific requirements, consider design tradeoffs, relate design decisions to IYFRs, justify the decisions, and assist defect detection. The purpose of this paper is to give an initial evaluation of the extent to which the framework's objectives are met. Three small portions of information systems were studied by the authors using the framework. The framework and empirical studies are evaluated herein, both from the viewpoint of domain experts who have reviewed the framework and studies, and ourselves as framework developers and users. The systems studied have a variety of characteristics, reflecting a variety of real application domains, and the studies deal with three important classes of NFRs for systems, namely, accuracy, security, and performance. The studies provide preliminary support for the usefulness of certain aspects of the framework, while raising some open issues. Although Non-Functional Requirements (NFRs) are recognized as very important contributors to the success of software projects, studies to date indicate that there is still no general consensus in the software engineering community regarding the notion of NFRs. This paper presents the result of an extensive and systematic analysis of the extant literature over three NFRs dimensions: (1) definition and terminology; (2) types; and (3) relevant NFRs in various types of systems and application domains. Two different perspectives to consider NFRs are described. A comprehensive catalogue of NFRs types as well as the top five NFRs that are frequently considered are presented. This paper also offers a novel classification of NFRs based on types of systems and application domains. This classification could assist software developers in identifying which NFRs are important in a particular application domain and for specific systems. Nonfunctional requirements (NFRs) have been frequently neglected or forgotten in software design. They have been presented as a second or even third class type of requirement, frequently hidden inside notes. We tackle this problem by treating NFRs as first class requirements. We present a process to elicit NFRs, analyze their interdependencies, and trace them to functional conceptual models. We focus our attention on conceptual models expressed using UML (Unified Modeling Language). Extensions to UML are proposed to allow NFRs to be expressed. We show how to integrate NFRs into the class, sequence, and collaboration diagrams. We also show how use cases and scenarios can be adapted to deal with NFRs. This work was used in three case studies and their results suggest that by using our proposal we can improve the quality of the resulting conceptual models.