In digital libraries accessing distributed Web-based bibliographic repositories, efficient query processing requires an advanced caching mechanism to reduce the query response time. Unfortunately, standard page-based and tuple-based caching mechanisms designed for conventional databases are not efficient on the Web, where keyword-based querying is often the only way to retrieve data. In this article, we study the problem of semantic caching of Web queries. We develop a caching mechanism for conjunctive Web queries based on “signature files”. We propose two implementation choices. A first algorithm copes with the relation of semantic containment between a query and the corresponding cache items. A second algorithm extends this processing to more complex cases of semantic intersection. We report results of experiments and show how the caching mechanism is realized in the Knowledge Broker system.

