Query processing in distributed, taxonomy-based information
We address the problem of answering queries over a distributed information system, storing objects
indexed by terms organized in a taxonomy. The taxonomy consists of subsumption relationships between
negation-free DNF formulas on terms and negation-free conjunctions of terms. In the first part of the
paper, we consider the centralized case, deriving a hypergraph-based algorithm that is efficient in data
complexity. In the second part of the paper, we consider the distributed case, presenting alternative ways
implementing the centralized algorithm. These ways descend from two basic criteria: direct vs. query
re-writing evaluation, and centralized vs. distributed data or taxonomy allocation. Combinations of
these criteria allow to cover a wide spectrum of architectures, ranging from client-server to peer-to-peer.
We evaluate the performance of the various architectures by simulation on a network with O(104
and derive final results. An extensive review of the relevant literature is finally included.