Identifying Reusable Services in Legacy Object-Oriented Systems: A Type-Sensitive Identification Approach

The migration of legacy software systems to a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">service-oriented architecture</i> (SOA) is one of the main strategies for modernising such systems. The success of modernising a legacy system to a SOA highly depends on the used service identification approach where the goal is to identify reusable functionalities that could become services. In this paper, we perform a comparative analysis of service identification approaches proposed by academia and industry. We show that there is a gap between academia and industry in the used approaches to identify services from legacy systems. We extract from the comparative analysis several recommendations about the inputs, processes, and outputs that a service identification approach should have. Based on these recommendations, we propose <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ServiceMiner</i>, a bottom-up service identification approach, which relies on source-code analysis, because other sources of information may be unavailable or out of sync with the actual code. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ServiceMiner</i> relies on a categorisation of service types and code-level patterns characterising types of services. We evaluate <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ServiceMiner</i> on four case studies. We also compare our results to those of three state-of-the-art approaches. We show that <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ServiceMiner</i> identifies architecturally-significant services with, on average, 78% precision, 76% recall, and 77% F-measure.