Web Services are considered as a dominant paradigm for constructing and composing distributed business application and enabling enterprise-wide interoperability. A peer to peer architecture provides a decentralized infrastructure in sync with the spirit of the web and that scales well to its size. In this paper, we present a framework enabling implicit i.e. dynamic service calls in data centric Peer to Peer Active XML language. Active XML is a language devoted to the management of distributed data by embedding Web service calls into XML document. The aim of implicit calls is to allow dynamic data sources discovery through dynamic services discovery and composition. Implicit service calls are based on the use of ontologies for describing the domain and functionality of services to call and an Active XML engine for the call evaluation. The evaluation process deals mainly with dynamic service composition. It consists of matching OWLS descriptions defined in a query with service descriptions in a peer-to-peer network. Such a network is structured in such a way that peers with similar functionalities are grouped together and each peer makes itself acquainted with matching relationships between its inputs/outputs and those of other peers.