It had always been the intention of the agent-based manufacturing community that software agents would provide a vertical integration capability for manufacturing enterprises by linking the control world with the business world. In this paper, we introduce the PROSA/G conceptual model, which extends the widely used PROSA reference architecture with a goal-based execution model that employs both BDI semantics and a business process modelling metaphor. PROSA/G is is grounded in the GORITE software framework and its efficacy is demonstrated through the implementation of an agent-based execution system for a simple manufacturing system controlled by IEC 61499 function blocks.