Distributed software systems need to evolve according to the ever-changing requirements on which they were built. Software systems' tailorability can be achieved in terms of component software. Atoms and molecules the basic constructs of the ATOMA framework, are the building blocks for distributed tailorable component-based software systems. These constructs can be considered as independent agents, that communicate in terms of, unanticipated, connections that are established at run-time, thus forming agent communities. System tailorability can take place at two levels. In high level tailorability whole parts of the functionality of a system, represented as agents, can be altered in order to provide new functionality. At a lower level, the tailorability of an agent itself, that is the tailorability of its functionality, is achieved through a flexible service mapping implementation for rule-based method invocation.