Most medium to large organizations support large collections of process designs, often stored in business process repositories. These processes are often inter-dependent. Managing such large collections of processes is not a trivial task. We argue that formalizing and establishing inter-process relationships play a critical role in that task leading to a machinery approach in the process repository management. We consider and propose three kinds of such relationships, namely part-whole, inter-operation and generalization-specialization, including their formal definitions, permitting us to develop a machinery approach. Analysis of the relationships relies on the semantically effects annotated process model in BPMN. This paper presents a rigorous approach to assist the designer to establish inter-process relationships in a process repository.