Existing ERP systems provide an IT solution to the management of enterprise resources based on the function-oriented management approach. With an increasingly wide adoption of the project-oriented management, new models are needed for ERP systems to support the management of enterprise resources in a project-oriented manner. This paper presents an architecture of an ERP system supporting project-oriented management. Two characteristics of the project-oriented management are integrated in the proposed architecture: first, social protocols are used to model interactions between actors (humans or software agents) within a given group. Second, the concept of group actions is detailed as a way to integrate group dynamics to social protocols.