This paper describes a framework for formalising tactical reasoning in dynamic multi-agent systems, populated by synthetic (software) agents. The proposed framework is based on a hierarchy of synthetic agent architectures and is expressive enough to capture a subset of desirable properties from both the situated automata and subsumption-style architectures, while retaining the rigour and clarity of logic-based possible worlds semantics. This framework is successfully realised in the RoboCup Simulation League domain. Not only did it provide a solid design approach to object-orientation, but it also enabled incremental implementation and testing of software agents and their modules. In particular, the framework allowed us to correlate enhancements in the agent architecture with tangible improvements in team performance. Cyberoos98 was 3rd place winner of the Pacific Rim series at PRICAI-98. Cyberoos99 finished in the top 18 of the RoboCup-99.