The recent trend on distributed and autonomous management of knowledge poses a new challenge concerned with the mapping between the representations of two sources of knowledge. While the number of solutions to this problem is growing in the scientific community there is still a lack of a common evaluation method. The objective of this work is to propose a framework to evaluate new competing solutions without any assumption on the mapping techniques. In the paper it will be argued that a viable way to proceed is to acquire an annotated collections of knowledge representations where the annotation can be conceived as an association between a set of objects and a set of concepts. The general problem of ontologies interoperability will be focused to a specific scenario of information retrieval.