Enriching Specifications to Represent Quality in Web Services in a Comprehensive Way

Quality is an important issue for WS-based software systems, like for any other software system. Quality is intrinsically a multi-faceted concept and is usually defined in terms of several quality attributes, quantified via a number of measures. In addition, relations may exist among the different quality attributes and among their measures. A quality attribute may positively or negatively influence another quality attribute. Each stakeholder needs to be able to evaluate the quality attributes that are of interest in his or her applications for his or her goals. For instance, WS users can evaluate specific quality attributes to decide whether to use a WS. WS providers can use quality attributes to set quality goals for a WS so that Service Level Agreements are satisfied. However, a limited number of qualities of individual and composite web services have been studied so far, e.g., reliability, response time, and availability. In addition, none of the available specifications are able to describe the relations among the different quality attributes. In this paper, we introduce a comprehensive approach to representing quality attributes in WS. While compatible with existing specifications defined by OASIS, our representation adds several important elements that take into account a number of important developments in the Software Measurement research and practice. Our representation proposal therefore enriches these specifications and provides a comprehensive reference model that can be used to syntactically specify internal and external quality attributes and their measures, along with their characteristics and relations. Our proposal is also compatible with the theoretical aspects required by the general literature on Measurement and with the ISO/IEC25010 quality standard.