CLASSIC: a structural data model for objects
SIGMOD '89 Proceedings of the 1989 ACM SIGMOD international conference on Management of data
LaSSIE: a knowledge-based software information system
Communications of the ACM - Special issue on software engineering
Taxonomic syntax for first order inference
Proceedings of the first international conference on Principles of knowledge representation and reasoning
KRIS: Knowledge Representation and Inference System
ACM SIGART Bulletin - Special issue on implemented knowledge representation and reasoning systems
On taxonomic reasoning in conceptual design
ACM Transactions on Database Systems (TODS)
Loading data into description reasoners
SIGMOD '93 Proceedings of the 1993 ACM SIGMOD international conference on Management of data
Subsumption between queries to object-oriented databases
Information Systems - Special issue on extending database technology
On the expressive power of datalog: tools and a case study
PODS '90 Proceedings of the ninth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Classification as a Query Processing Technique in the CANDIDE Semantic Data Model
Proceedings of the Fifth International Conference on Data Engineering
Knowledge Mining by Imprecise Querying: A Classification-Based Approach
Proceedings of the Eighth International Conference on Data Engineering
Entity-Situation: A Model for the Knowledge Representation Module of a KBMS
EDBT '88 Proceedings of the International Conference on Extending Database Technology: Advances in Database Technology
An optimal lower bound on the number of variables for graph identification
SFCS '89 Proceedings of the 30th Annual Symposium on Foundations of Computer Science
Concept languages as query languages
AAAI'91 Proceedings of the ninth National conference on Artificial intelligence - Volume 1
Description Logics in Data Management
IEEE Transactions on Knowledge and Data Engineering
A revision-based approach to handling inconsistency in description logics
Artificial Intelligence Review
What's in an attribute? consequences for the least common subsumer
Journal of Artificial Intelligence Research
Part-whole reasoning in an object-centered framework
Part-whole reasoning in an object-centered framework
Non-standard inferences in description logics
Non-standard inferences in description logics
The limits on combining recursive horn rules with description logics
AAAI'96 Proceedings of the thirteenth national conference on Artificial intelligence - Volume 1
Description and generation of computational agents
KSEM'06 Proceedings of the First international conference on Knowledge Science, Engineering and Management
Inconsistency-tolerant reasoning with OWL DL
International Journal of Approximate Reasoning
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Description languages form the basis of several object-centered knowledge base management systems developed in recent years, including ones in industrial use. Originally used for conceptual modeling (to define views), DLs are seeing increased use as query languages for retrieving information. This paper, aimed at a general audience that includes database researchers, considers the relationship between the expressive power of DLs and that of query languages based on Predicate Calculus.We show that all descriptions built using constructors currently considered in the literature can be expressed as formulae of the First Order Predicate Calculus (FOPC) with at most three variable symbols, though we have to allow numeric quantifiers and infinitary disjunction in order to handle some special constructors. Conversely, we show that all first-order queries (formulae with one free variable) built up from unary and binary predicates using at most three variables can be expressed as descriptions. We conclude by exhibiting queries that cannot be expressed as DL concepts, and reflecting briefly on consequences.