Waldinger, R., Reddy, M., Culy, C., Hobbs, J., and Dungan, J. Deductive Response to Geographic Queries, in GIScience 2002, Boulder, CO, Sep 2002.
When we have a question, there may be many sources of information, including programs and data, relevant to finding the answer. We may not know which sources are appropriate. They may reside on different machines in diverse locations. Knowledge may be represented according to different frameworks, notations, or coordinate systems. The answer may not exist anywhere explicitly; it may need to be inferred, and it may depend on more than one source.