Abstract and concrete categories
Abstract and concrete categories
A formal approach to object-oriented databases
Data & Knowledge Engineering
Inheritance, defaults and the lexicon
Inheritance, defaults and the lexicon
Description Logics in Data Management
IEEE Transactions on Knowledge and Data Engineering
Feature logic with disjunctive unification
COLING '90 Proceedings of the 13th conference on Computational linguistics - Volume 2
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Type hierarchies which arise in applications are often described incompletely; this missing information may be handled in a variety of ways. In this work, such incomplete hierarchies are viewed as open specifications; that is, descriptions which are sets of constraints. The actual hierarchy is then any structure satisfying these constraints. For such specifications, two forms of characterization are provided. The first is algebraic and utilizes a generalization of weak partial lattices; it provides a structure-based characterization in which optimality is characterized via an initial construction. The second is logical, an inference-based representation, in which models are characterized as products of models of propositional-based specifications.