Explanation trees in CONTEXT: a constraint explanation tool

Abstract

The organization and presentation of constraints within a constraint explanation tool known as CONTEXT is described. CONTEXT provides a means for transforming constraints into propagation rules for actively maintaining constraints. The focus is on the functionality of CONTEXT as a constraint explanation tool, describing a structure known as explanation trees. Explanation trees provide a basis for the presentation of constraints, the validation of constraint structures, the identification of propagation actions, and query processing for constraint checking at execution time. The primary contribution of explanation trees within CONTEXT is the manner in which they support the explanation of schema constraints from the point of view of any relevant database update operation.<>