XPath-Logic and XPathLog: A Logic-Programming Style XML Data Manipulation Language

TL;DR

This paper introduces XPathLog, a logic programming language for XML data that extends XPath with variables and rule-based querying, providing formal semantics and a declarative approach to XML data manipulation.

Contribution

It presents XPathLog as a Datalog-style extension of XPath with formal semantics, enabling declarative XML data querying and updates based on logic programming principles.

Findings

Defines a formal, logic-based semantics for XPathLog.

Provides an answer-set semantics for XPathLog queries.

Demonstrates XPathLog's capability for declarative XML data updates.

Abstract

We define XPathLog as a Datalog-style extension of XPath. XPathLog provides a clear, declarative language for querying and manipulating XML whose perspectives are especially in XML data integration. In our characterization, the formal semantics is defined wrt. an edge-labeled graph-based model which covers the XML data model. We give a complete, logic-based characterization of XML data and the main language concept for XML, XPath. XPath-Logic extends the XPath language with variable bindings and embeds it into first-order logic. XPathLog is then the Horn fragment of XPath-Logic, providing a Datalog-style, rule-based language for querying and manipulating XML data. The model-theoretic semantics of XPath-Logic serves as the base of XPathLog as a logic-programming language, whereas also an equivalent answer-set semantics for evaluating XPathLog queries is given. In contrast to other approaches, the XPath syntax and semantics is also used for a declarative specification how the database should be updated: when used in rule heads, XPath filters are interpreted as specifications of elements and properties which should be added to the database.