Enriching business process models with semantic tags taken from an ontology has become a crucial necessity in service provisioning, integration and composition. In this paper we propose to represent semantically labelled business processes as part of a knowledge base that formalises: business process structure, business domains, and a set of criteria describing correct semantic labelling. Our approach allows (1) to impose domain dependent constraints during the phase of process design, and (2) to automatically verify, via logical reasoning, if business processes fulfill a set of given constraints, and to formulate queries that involve both knowledge about the domain and the process structure. Feasibility and usefulness of our approach will be shown by means of two use cases. The first one on domain specific constraints, and the second one on mining and evolution of crosscutting concerns.