Date of this Version
D. Srivastava, R. Ramakrishnan, P. Z. Revesz, Constraint objects, Proc. Workshop on Principles and Practice of Constraint Programming, Springer LNCS 874, pp. 218--228, Orcas Island, Washington, USA, May 1994.
We describe the Constraint Object Data Model (CODM), which enhances an object-based data model with existential constraints to naturally represent partially specified information. We present the Constraint Object Query Language (COQL), a declarative, rule-based query language that can be used to infer relationships about and monotonically refine information represented in the CODM. COQL has a model-theoretic and an equivalent fixed-point semantics, based on the notions of constraint entailment and "proofs in all possible worlds." We also provide a novel polynomial-time algorithm for quantifier elimination for set-order constraints, a restricted class of set constraints that uses membership of subset-equal.