For example, one common library service is that of answering queries. A query planning service will, based upon the user's query, search the appropriate collections for relevant items, possibly employing a thesaurus or other indexing service. Query planning services may differentiate themselves through the different attributes associated with them, such as target audience (Professional, High School, Middle School), topic (Science, Art, Literature), and recommending organization (ACM, IEEE, National Education Association). Figure 1 shows a simple taxonomy of possible query planning audience and topic attributes.
Clearly High School audiences are just a particular kind of School audiences and Astronomy topics are a subclass of Science topics. Thus, a service that can respond to queries about High School Science will also be able to respond to queries about High School Astronomy. We discuss the opportunities, and special considerations, involved in using this sort of inferencing to match agents with markets in Section 3.1.
