Nam (Pierre) Huyn's Papers

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Constraint Checking Papers

Efficient Complete Local Tests for Conjunctive Query Constraints with Negation . Shows consistency-preserving updates can be efficiently detected when the relations under constraints are not completely given. The tests are given in the form of nonrecursive Datalog queries with negation. Also, a shorter version that appears In Proc. 6th Int. Conf. Database Theory, Athens, Greece, Jan 1997.

Maintaining Global Integrity Constraints in Distributed Databases . Cleans up the previous paper and extends the results to arbitrary mixes of insertions and arbitrary mixes of deletions. To appear in the Constraints journal special issue on Constraints and Databases, 1998.

View Self-Maintenance Papers

Efficient View Self-Maintenance . Strict view self-maintenance is the process of bringing a materialized view up to date when the base relations change, using only the view but NO base relations. The paper solves the problem for conjunctive-query views (no self-joins) with very simple queries. Also, a shorter version that appears In Proc. ACM Workshop on Materialized Views: Techniques and Applications, Montreal, Canada, June 1996.

Efficient Self-Maintenance of Materialized Views . Efficient solutions to the strict view self-maintenance problem are extended to conjunctive-query views with "exposed" self-joins. Efficient solutions to the view self-maintenance problem, when some of the base relations or auxiliary views are available, are also given. Also, a shorter version that was submitted for publication.

Multiple-View Self-Maintenance in Data Warehousing Environments . We solve the problem of view self-maintenance in the presence of multiple views and under arbitrary base updates. Strict and generalized self-maintenance are considered. We give insight to the self-maintainability problem by reducing it to a problem of instance-specific query containment. For a subclass of conjunctive-query views, we show how to solve the problem in polynomial time and in particular how to generate queries for maintenance and for testing self-maintainability. Also, a shorter version to appear In Proc. 23rd Int. Conf. VLDB, Athens, Greece, Aug. 1997.

Exploiting Dependencies to Enhance View Self-Maintainability . Shows functional dependencies are helpful to strict view self-maintenance. Efficient solutions are given. Also, a shorter version that was submitted for publication.

Information Integration Papers

Agent-Based Concurrent Engineering . In Proc. Concurrent Engineering & CALS Conf., Washington D. C., 1992 (with Michael Genesereth and Reed Letsinger). Describes a novel software framework that supports collaborative work in a federated system, in which individual components are modeled as software "agents".

Automated Concurrent Engineering in DesignWorld . In IEEE Computer, Special Issue on Computer Support for Concurrent Engineering, January 1993 (with Michael Genesereth and Reed Letsinger). Describes the integration problem in Designworld, a total engineering environment for the design and fabrication of digital systems, and its solution using an "agent" framework.

Query Reformulation under Incomplete Mappings . How do we answer queries expressed in terms of virtual views, when the mappings from the materialized views to virtual views are incomplete. When this incompleteness takes the form of existentially quantified sentences, the paper proposes an algorithm that rewrites a query to an "equivalent" query that only uses the materialized views. The algorithm essentially eliminates all functional symbols from a recursive Horn program.

A More Aggressive Use of Views to Extract Information . Answering queries using views essentially looks for exact "matches". When exact matches do not exists, the paper proposes the notion of "best matches" that always exists and can be computed. An algorithm is given that applies to recursive queries.