IDS-Constrained Text-To-Graph Querying for IFC Models

Accessing Building Information Model (BIM) data en- coded in Industry Foundation Classes (IFC) remains difficult for non-expert stakeholders due to heteroge- neous property sets and nested relationships. This pa- per presents a constrained text-to-graph querying frame- work that transforms IFC data into a labeled property graph, queried via Cypher, while project-specific Infor- mation Delivery Specification (IDS) requirements define admissible entity labels, relationships, and property keys. A regular-expression grammar restricts Large Language Model (LLM) generation to executable, schema-compliant queries. Evaluation shows grammar constraints eliminate schema hallucinations, achieving 100% Semantic Compli- ance and improved execution accuracy, with competitive performance from smaller open-weights models.