The literature review contains a comprehensive picture of related work carried out, including a critical analysis of existing software architecture assessment methods/frameworks used to ensure quality of service in the software architecture. This also reflects the limitations of existing models and provides motivation for further research in the same area. This chapter has been classified into four subsections according to the specific aspects of the research area. 2.1 Quality attributes and quality model An important issue in software development today is quality. The non-functional characteristics of a component or system are called quality attributes. “Software quality is defined in IEEE 1061 and represents the degree to which the software possesses a desired combination of attributes” [1]. A software quality model is defined in the ISO/IEC 9126-1 project [2]. Functionality, reliability, usability, efficiency, maintainability and portability are the six fundamental categories of software architecture characteristics that are divided into sub-characteristics according to this software quality model. A large number of definitions of quality attributes exist in the literature. For example, the definitions of maintainability, flexibility and modifiability are described as follows [3]. “Maintainability is a set of attributes that affect the effort required to make specified changes” [2]. Corrections, improvements or adaptations of software to changes in environment, requirements and functional specifications are part of maintainability. “Modifiability is the ability to make changes quickly and cost-effectively” [4]. There are two types of system modifications: extensibility, portability, and restructuring. Extensibility o...... middle of paper ...... CarrieÁre, ªThe method of analyzing architectural trade-offs,º Proc. Fourth Conf. international. Eng. of Complex Computer Systems (ICECCS '98), August 1998.[25]. M. Barbacci, S. Carriere, P. Feiler, R. Kazman, M. Klein, H. Lipson, T. Longstaff, and C. Weinstock, “Steps in a Method for Analyzing Architectural Tradeoffs: Models and Analyzes of quality attributes”, technical report, CMU/SEI-97-TR-029 ESC-TR-97-029, 1998.[26]. P. O. Bengtsson and J. Bosch, “Scenario-based architecture reengineering,” Proc. Fifth Conf. international. Software Reuse (ICSR 5), 1998.[27]. P. O. Bengtsson and J. Bosch, “Architecture level prediction of software maintenance,” Proc. Third Conf. European. Software Maintenance and Reeng., pp. 139-147, March 1999.[28]. JC Duenas, WL de Oliveira and JA de la Puente, ªA software architecture evaluation model,º Proc. Second international ESPRIT ARES workshop, pp. 148-157, February. 1998.