MODELS OF A DISTRIBUTED INFORMATION-RETRIEVAL SYSTEM BASED ON THESAURI WITH WEIGHTS

The problem of combining n local information systems S1, S2,...,S(n) based on thesauri with weights in one system S is considered. The distributed information retrieval system S may be assumed to be a network of the local systems S(j). Both the generalization relation on the set of descriptors and weights of descriptors in descriptions of documents are taken into account. The fundamental properties of distributed systems are described. The inverted file structure is often used to organize data in the information retrieval system. Operations on inverted lists are modified in order to use them in the distributed information system. While retrieving the response to any query in a distributed system, we may use the existing inverted lists from local subsystems. In a distributed system the retrieval process follows almost in the same way as in the method of inverted files in conventional systems. It differs only due to use of the additional union operations on selected inverted lists from any local subsystems. The presented retrieval rules may be viewed as the logical approach in implementing a physical distributed information retrieval system.