Traders serve as mediators between service providers and users. The trader returns to a service requester by delivering a set of suitable providers that satisfy the request. Because of the size and complexity of distributed systems, one trader manages a certain part of the whole set of providers only. To enlarge this restricted set of potential service providers, a lightweight form of cooperation (called interworking) between two or more traders was introduced. Therefore, the main purpose of such cooperations was concerned with quantitative aspects, neglecting the possibilities of more general concepts of cooperation. A need for qualitative trader cooperations arises. Traditional trader approaches focus upon the operational interface of providers as a basis for type descriptions. But in general, application users in an open electronic market require mediation at different levels of abstraction. Suitable traders are specialized in one of these levels. By combining these isolated solutions, a qualitative trader cooperation can be achieved.

In the following, we take a closer look at type descriptions at different levels of abstraction. Similarities will be discovered that can be used to derive appropriate mappings. In particular we demonstrate that ODP--types based on an arbitrary interface definition language can be described in terms of conceptual graphs that are used in knowledge--based trading. From this relationship, a general type manager can be derived, coping with both type concepts. As a consequence, the trading of operational interfaces and the trading based on a knowledge representation scheme can be combined. Together they exhibit a more powerful trading service by offering different interfaces to different kinds of users.