Comparing the impact of service-oriented and object-oriented paradigms on the structural properties of software

Service-Oriented Architecture (SOA) is a promising approach for developing enterprise applications. While the concept of SOA has been described in research and industry literature, the techniques for determining optimal granularity of services and encapsulating business logic in software are unclear. This paper explores this problem using a case study developed with two contrasting approaches to building enterprise applications that utilise services, where one of the approaches employs coarse-grained services developed based on the principles of Object-Orientation (OO), and another approach is based on embedding business rules and logic into executable BPEL scripts and constructing a system as a set of fine-grained services. The quantitative comparison based on a set of mature software engineering metrics showed that a system developed using the BPEL-based approach has a potentially higher structural complexity, but at the same time lower coupling between software modules compared to an OO approach. It was also shown that some of the existing software metrics are inapplicable to SOA, hence new metrics need to be developed