Resource Assignment Language (RAL) is a language for the selection of organisational resources that can be used, for example, for the assignment of human resources to business process activities. Its formal semantics have allowed the automation of analysis operations in several phases of the business process lifecycle. RAL was designed considering a specific organisational metamodel and pursuing specific purposes. However, it can be extended to deal with similar problems in different domains and under different circumstances. In this paper, a methodology to extend RAL is introduced, and an extension to support another organisational metamodel is described as a proof-of-concept.