Abstract
Service-Oriented Architectures (SOA) provide the first widely applicable approach to tying together diverse "stovepipe" (or "silo") systems. They are, therefore, a "pure" example of how to build Systems of Systems (SOS). With the growing interest in and increasing number of implementations of SOAs, there is a pressing need for measures and metrics that can help SOA developers (Chief Architects or Program Managers) in predicting potential problems in the development/evolution of their SOA system. For SOA-based systems, such assistance is vital since their success depends on melding appropriate technologies and design with organizational characteristics, customer profiles, and functions provided, a Systems of Systems (SOS) concern. This paper discusses an ongoing effort in this area. In addition to providing a useful tool, this effort is technically significant for three key reasons. First, SOA specification and assessment requires consideration of technology factors and their relationships to the organization, and to individual information consumers. Essentially, these are related to metrics for systems engineering. Second, requirements (e.g., ease of use, flexibility) are defined in terms of system characteristics that can be modeled and measured. Thus, the system is defined by a set of evolving models and metrics that allow continual evaluation of progress towards eliminating problems. Third, since requirements are initially expressed with coarse-grained conceptual models, measurement of the characteristics of these models can indicate areas where the system might not meet some requirement, thereby allowing early corrective action. Thereafter, more refined models, can be developed to track the success of corrective actions. This paper provides a background on SOA, challenges for SOA metrics, and proposes a model-based metrics framework for evaluating SOAbased systems on an ongoing basis. It provides exemplar metrics and measures for SOA, and discusses several approaches to metrics quantification and presentation.