A unified constraint model for XML
Wenfei Fan, Gabriel M. Kuper, Jérǒme Simèon · 2001
Integrity constraints are an essential part of modern schema denition languages. They are useful for semantic specication, update consistency control, query optimization, information preservation, etc. In this paper, we propose UCM, a model of integrity constraints for XML that is both simple and expressive. Because it relies on a single notion of keys and foreign keys, the UCM model is easy to use and makes formal reasoning possible. Becauseitreliesonapowerful type system, the UCM model is expressive, capturing in a single framework the constraints found in relational databases, objectoriented schemas and XML DTDs. We study the problem of consistency of UCM constraints, the interaction between constraints and subtyping, and algorithms for implementing these constraints. Keywords XML, XML Schema, Integrity Constraints, Keys, Object Identity, Subtyping, Constraint Reasoning 1.