Service-oriented manufacturing systems need to be supported by formal reference models for effective service description, discovery, and composition. A reference model should evolve continuously throughout its lifecycle to respond to changing requirements. The objective of this work is to propose a formal process for collaborative and community-based reference-model evolution and identify the computational components required for effective model evolution. The main steps of the proposed process include service registration, vocabulary extraction, evolution triggering, change evaluation and approval, and change implementation. An important feature of the proposed process is the use of a Simple Knowledge Organization System (SKOS) thesaurus for the initial stages of knowledge elicitation and organization.