Designers of collaboration systems address many interrelated issues in a social-technical context. The volume, complexity, and variety of issues can invoke cognitive overload, causing deficiencies in system designs. We use inductive logic to derive seven key areas of concern for designers of collaboration support systems. We use deductive logic to argue that these areas address collaboration at differing levels of abstraction, and so may be organized into a seven-layer model, affording separation of concerns at design time. The layers are: Goals, Products, Activities, Patterns, Techniques, Tools, and Scripts. Design changes at one layer may not necessitate changes to layers above it, but may require changes to layers below it. At each layer and between each layer there are different issues and outcomes that may be addressed with different concepts, techniques and tools. This separation of concerns may reduce cognitive load for designers and may help to improve completeness and consistency of their designs, yielding higher productivity for collaborating groups.