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; resulting in an implementation of a heterogeneous soccer team of autonomous software agents. 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. The Cyberoos98 played 7 official Simulation League games in 1998; winning 4 of them (3rd place winner of the Pacific Rim series at PRICAI-98).