Considers a "hybrid" approach to the modeling of uncertainty in deductive databases. The model, deductive IST (DIST) is based on an extension of the "Information Source Tracking" (IST) model for relational databases. Proves that the complexity of testing containment of conjunctive DIST queries remains the same as in the…

Presents a seven-step methodology for utilizing integrity constraint knowledge from heterogeneous databases. Describes generating a set of integrity constraints applicable at the integrated level from constraints specified on local databases. Introduces the concept of constraint-based relationships between objects in heterogeneous databases;…

Presents three different statistical techniques for identifying content-bearing phrases within a natural language database. Describes results on the effectiveness of the scoring methods when applied to MEDLINE phrases, and how the three methods can be combined to improve performance. Processing results for an example document are provided.…

Discussion of users and information retrieval systems highlights a study that investigated the representation of users' knowledge by examining their names for objects and concepts, agreement on names, the Library of Congress Subject Headings representation for similar objects and concepts, and measurement of the similarity between these…

Reports on two studies in the second Text Retrieval Conference (TREC-2) program that investigated the effect on retrieval performance of combination of multiple representations of TREC topics. Six methods of query combinations and the combination of the same queries on different databases are examined. Results show that combining evidence from…

Describes and evaluates a system that selects key information from an event database by reasoning about event frequencies, frequencies of relations between events, and domain-specific importance measures. The system aggregates similar information and plans a summary tailored to a stereotypical user. (AEF)

Computer-Supported Intentional Learning Environments (CSILE) is a database system in which learners collaboratively construct the knowledge represented in the database. This study examines how students in a grade-five and -six classroom built their database on a science topic, electricity. Differences in cognitive and operative activities between…