NaVQA: Mitigating Silent Failures in Question Answering over Virtual Knowledge Graph

摘要

Virtual Knowledge Graphs (VKGs) provide unified access to legacy relational data sources through a high-level ontology modeling a domain of interest. The content of the ontology elements (classes and properties) is virtually mapped to underlying data sources through declarative mappings. The standard approach to interacting with a VKG system is to use SPARQL as the query language. However, the complexity of SPARQL creates a high entry barrier for normal users. In this paper, we study the VKG-QA task, which enables users to interact with the VKGs through a natural language (NL) interface by translating their questions into SPARQL queries. One critical challenge in such translation is silent failures, where a syntactically correct SPARQL query returns empty results because it involves ontology elements that lack mappings to the underlying data. To address this, we propose NaVQA (Navigation-based VKG Question Answering), a framework leveraging Large Language Models that (1) identifies and indexes the active ontology elements based on the mapping specifications, and (2) iteratively constructs a query graph from the NL question using the active ontology elements and their relations to synthesize SPARQL. Experiments on three real-world VKGs show that NaVQA significantly mitigates silent failures and outperforms existing baselines.