Towards a theory of Fa\c{c}ade-X data access: satisfiability of SPARQL basic graph patterns

2026-02-12

AI Summary

This work addresses the lack of theoretical foundations and decision procedures for the satisfiability of Basic Graph Patterns (BGPs) in Façade-X, a framework that enables SPARQL querying over heterogeneous data sources. To bridge this gap, the paper presents the first formal theory for BGP satisfiability in Façade-X, introducing a logical analysis framework grounded in an RDF metamodel and an efficient decision algorithm. A prototype system implementing the proposed approach is developed and evaluated. Experimental results demonstrate that the method effectively handles real-world queries and significantly improves query execution efficiency, thereby filling a critical theoretical void in semantic analysis for SPARQL-based heterogeneous data integration.

Technology Category

• Constraint Satisfaction and Optimization: Satisfiability Modulo Theories
• Knowledge Representation and Reasoning: Description Logics
• Data Mining & Knowledge Management: Intelligent Query Processing

Application Category

• Graph Algorithms and Modeling for the Web: Querying, indexing, and retrieval in Web-related graphs
• Semantics and Knowledge: Methods, algorithms and applications for the development of semantic models, knowledge graphs and other forms of structured data models with machine-interpretable semantics
• Search and Retrieval-Augmented AI: Web query analysis, representation and understanding

Abstract

Data integration is the primary use case for knowledge graphs. However, integrated data are not typically graphs but come in different formats, for example, CSV, XML, or a relational database. Fa\c{c}ade-X is a recently proposed method for providing direct access to an open-ended set of data formats. The method includes a meta-model that specialises RDF to fit general data structures. This model allows to express SPARQL queries targeting data sources with those structures. Previous work formalised Fa\c{c}ade-X and demonstrated how it can theoretically represent any format expressible with a context-free grammar, as well as the relational model. A reference implementation, SPARQL Anything, demonstrates the feasibility of the approach in practice. It is noteworthy that Fa\c{c}ade-X utilises a fraction of RDF, and, consequently, not all SPARQL queries yield a solution (i.e. are satisfiable) when evaluated over a Fa\c{c}ade-X graph. In this article, we consolidate Fa\c{c}ade-X, and we study the satisfiability of basic graph patterns. The theory is accompanied by an algorithm for deciding the satisfiability of basic graph patterns on Fa\c{c}ade-X data sources. Furthermore, we provide extensive experiments with a proof-of-concept implementation, demonstrating practical feasibility, including with real-world queries. Our results pave the way for studying query execution strategies for Fa\c{c}ade-X data access with SPARQL and supporting developers to build more efficient data integration systems for knowledge graphs.

Problem

• Façade-X
• SPARQL
• satisfiability
• basic graph patterns
• data integration

Innovation

• Façade-X
• SPARQL satisfiability
• basic graph patterns
• data integration
• knowledge graphs