Multi-Agent Systems (MAS) have become increasingly mature, but this maturity does not make the traditional Object Oriented (OO) approaches obsolete. On the contrary, building MAS in combination with OO constructs allows the reuse of components. Similarly, OO methodologies can benefit from extension towards an agent abstraction and so make use of the methods and tools for MAS. The Agent-Rule-Class (ARC) framework is proposed as an approach that builds agents upon traditional OO system components and makes use of business rules to dictate agent behaviours, aided by the OO components. By modelling agent knowledge in business rules, the proposed paradigm provides a straightforward means to develop agent-oriented systems based on the existing object-oriented systems and offers features that are otherwise difficult to achieve in OO systems. A Structural Model and a Behavioural Model are the central components in the ARC framework for agent-oriented system modelling. A supporting tool has bee...