Systematic construction of quality models for cots-based systems

In this thesis we present the COSTUME method aimed at the construction of COTS-based system quality models, The method describes a set of activities which allow the construction of system level quality models, by composing individual quality modes of its constitutive system actors. The method is supported by a set of knowledge repositories, which are intended to abstract and store several of the deliverables obtained in the process and allow for their future reuse. The method proposes four main activities to drive quality models construction with a well defined rationale which increases the efficiency of the process whilst improving the reliability of the deliverables. Resulting quality models include quality features that have been proposed in the literature and also refine some of them. Quality models are constituted by a set of high-level quality characteristics (the ones proposed in the ISO/IEC 9126-1 quality standard), and hierarchies of subcharacteristics and quality attributes (basic and derived), for which COTS systems can be evaluated using the appropriated metrics. Relationships among quality features (other than hierarchical ones), are also included in the quality models to improve their applicability. The first activity of COSTUME is intended to define a model of the system and its environment; to do so, agent modeling techniques are used, namely Yu's [Yu95] i* modeling approach. In the second activity, five steps are used to explore and detail the insides of the system. An i* SR system model is constructed and the goals and sub-goals included in the model are grouped into system actors. System actors define atomic COTS domains for which COTS components can be identified. System actors are not expected to be mapped in one-to-one base to COTS components; the main purpose for their identification, in our case, is that they define the domains for which individual quality models are to be constructed. Activity 3 of the COSTU