Enterprise modelling (EM) methods are well-recognised for its value to describe a complex, informal domain in an organised structure. EM methods are used in practice, particularly during the early stages of software system development, e.g. during the phase of business requirements elicitation. The built model, however, has not always provided direct input to develop software systems. Despite the technical problem that adequate trainning is required to understand and use EM methods, informality that are largely seen in enterprise models presents a main obstacle. This talk focuses on one type of EM methods: business process modelling methods. It merges two main and complimentary business process representations, IDEF3 and PSL, to provide a Fundamental Business Process Modelling Language(FBPML) that is designed for simplicity to use and underpinned with rich underlying formality that may be used directly to support software and workflow system development.