Evo-DKD: Dual-Knowledge Decoding for Autonomous Ontology Evolution in Large Language Models

Abstract: Ontologies and knowledge graphs require continuous evolution to remain comprehensive and accurate, but manual curation is labor intensive. LLMs possess vast unstructured knowledge but struggle with maintaining structured consistency. We propose Evo-DKD, a novel dual-decoder framework for autonomous ontology evolution that combines structured ontology traversal with unstructured text reasoning. Evo-DKD introduces two parallel decoding streams within an LLM: one decoder generates candidate ontology edits (e.g., new concepts or relations) while the other produces natural-language justifications. A dynamic attention-based gating mechanism coordinates the two streams, deciding at each step how to blend structured and unstructured knowledge. Due to GPU constraints, we simulate the dual-decoder behavior using prompt-based mode control to approximate coordinated decoding in a single-stream mode. The system operates in a closed reasoning loop: proposed ontology edits are validated (via consistency checks and cross-verification with the text explanations) and then injected into the knowledge base, which in turn informs subsequent reasoning. We demonstrate Evo-DKD's effectiveness on use cases including healthcare ontology refinement, semantic search improvement, and cultural heritage timeline modeling. Experiments show that Evo-DKD outperforms baselines using structured-only or unstructured-only decoding in both precision of ontology updates and downstream task performance. We present quantitative metrics and qualitative examples, confirming the contributions of the dual-decoder design and gating router. Evo-DKD offers a new paradigm for LLM-driven knowledge base maintenance, combining the strengths of symbolic and neural reasoning for sustainable ontology evolution.