The need for having interoperable systems despite the presence of heterogeneous platforms has resulted in tremendous growth and acceptance of Web Services in recent years. This success of Web Services technology is fueling research efforts towards generalization into a science for Service Oriented Computing (SOC). However, beyond the basic publish-find-bind model there is not much consensus yet on what are the architectural building blocks of a Service Oriented Architecture (SOA). In this paper, we present a semantic model for SOC that is based upon established and well proven techniques of object oriented paradigm.