Requirements for a layered software architecture supporting cooperative multi-user interaction

Layered interactive systems lend themselves to be adapted for cooperation if inter-layer communication is charged to separated connectors. Point-to-point connectors can be replaced with cooperative connectors multiplexing and demultiplexing I/O between a particular layer and multiple instances of the next lower one. For this technique to be most effective, some general guidelines should be followed that support the design of good quality software where discrimination between heterogeneous functionality at the architectural level allows multiple interacting users to exploit different system features based on their role in the cooperation. This provides a sound basis for augmenting collaboration-transparent layered systems with powerful collaboration support (e.g. complex coordination policies) yet preserving separation of concerns between applicative and cooperative functionality. The paper discusses these issues both in general and with reference to their application within the CSDL framework for cooperative systems design.