An important task in Enterprise Application Integration (EAI) is to resolve syntactic and semantic heterogeneity. Especially difficult the latter is. Some existing integration approaches have been criticized for their lack of semantic richness. They focus mainly on the technical and syntactical integration. To overcome these limitations, this paper introduces novel ontology based architecture to ensure both sides of integration: inside Application to Application (A2A) and outside Business to Business (B2B), in order to support larger scale of integrations. Our proposal includes two important parts. First, we suggest an integration process basing on mapping approach to bridge applications ontologies. Second, we introduce an approach to build business process ontology using web services composition strategy and an integration scenario. We also use BPEL4WS language as a specification language for expressing business process control flow and constraints.