Service discovery has been recognised as an important activity for service-based systems. In this paper we describe a framework for dynamic service discovery that supports the identification of service during the execution time of service-based systems. In the framework, services are identified based on structural, behavioural, quality, and contextual characteristics of a system represented in query languages. The framework supports both pull and push modes of query execution. In the approach, a service is identified based on the computation of distances between a query and a candidate service. A prototype tool has been implemented in order to illustrate and evaluate the framework. The paper also describes the results of a set of experiments that we have conducted to evaluate the work.