View Updatability Checking with Simulation-based Graph Schema

Abstract

A view denotes some information extracted from a database through a transformation, and the view updating problem is concerned with translating a view update into a corresponding update against the base data source. The view updating problem, originated from the database community, is gaining more and more interest from the researchers in the programming community. In our previous work, we solve the view updating problem in which both sources and views are represented by graph-structured data for general purposes. However, there is a problem; the backward computation may be in vain when the updated view is invalid in the sense that either there is no candidate of corresponding sources or the corresponding source does not conform to user's intention. In this paper, we present a method for checking view updatability in order to know whether the updated view is valid or not before computing the corresponding sources. To achieve a simple computation of view updatability checking, we introduce a new graph schema whose conformance is defined by graph simulation. Although the idea of our schema comes from the simulation-based graph schema proposed by Buneman et al., our schema can describe necessity of outgoing edges, which was impossible in their schema. This improvement helps us to give more precise solution for view updatability checking.