Rewrite based Verification of XML Updates

TL;DR

This paper presents a method for verifying XML document updates by reducing access control and safety property checks to hedge automata type checking, ensuring document validity after updates.

Contribution

It introduces a novel approach to static type checking for XML updates using hedge automata, addressing safety and policy consistency problems.

Findings

Type checking reduces to hedge automata computations

Ensures preservation of document types after updates

Detects policy violations through automata analysis

Abstract

We consider problems of access control for update of XML documents. In the context of XML programming, types can be viewed as hedge automata, and static type checking amounts to verify that a program always converts valid source documents into also valid output documents. Given a set of update operations we are particularly interested by checking safety properties such as preservation of document types along any sequence of updates. We are also interested by the related policy consistency problem, that is detecting whether a sequence of authorized operations can simulate a forbidden one. We reduce these questions to type checking problems, solved by computing variants of hedge automata characterizing the set of ancestors and descendants of the initial document type for the closure of parameterized rewrite rules.