Why Your Agent's Brain Needs a Playbook: Practical Wins from Using Ontologies - Jesús Barrasa, Neo4j

Original: Why Your Agent’s Brain Needs a Playbook: Practical Wins from Using Ontologies - Jesús Barrasa, Neo4j

1.9K views · Jun 27, 2025 · 13:53 min · Watch on YouTube ↗

Takeaway

Ontology-driven graphs give GraphRAG pipelines a shared schema that produces better extraction, retrieval, and structured query generation than ad-hoc per-pipeline schemas.

Summary

GraphRAG replaces vector DB with a Neo4j knowledge graph: nodes (entities), directed relationships, properties (incl. vector embeddings on chunks)
Property graph has 'domain graph' + 'lexical graph' (document/chunk structure); entity extraction links chunks to entities for provenance-aware retrieval
Ontologies (e.g. FIBO financial ontology, W3C standards) provide implementation-agnostic schemas that drive both structured-to-graph and unstructured-to-graph pipelines
Better ontology-driven graphs improve text-to-Cypher accuracy and vector+context retrieval quality (completeness, precision, faithfulness)

graph-ragontologyneo4j

Original description

You're trying to guide how your agents think and act. Code-orchestrated workflows are too rigid, but LLMs charting their own course feel too chaotic. When you need a middle ground, it’s time to reach for the secret weapon: ontologies. These graph-shaped fragments of actionable knowledge can fill in critical gaps.

In this talk, we’ll explore together how ontologies bring structure, semantics, and sanity to GenAI-powered applications. You’ll learn when they’re useful, how to apply them, and what kinds of problems they help solve. Through practical examples, we’ll show how ontologies (1) guide knowledge graph construction, (2) add a semantic layer for more efficient and accurate retrieval (GraphRAG), and (3) encode domain logic you don’t want to leave up to the LLM.

About Jesús Barrasa
Dr. Jesús Barrasa is the AI Field CTO at Neo4j, where he works with organisations combining the power of GenAI with Knowledge Graphs. He co-authored "Building Knowledge Graphs" (O'Reilly 2023) and is cohost of the monthly Going Meta live webcast (https://goingmeta.live/) since 2022.
Jesús holds a Ph.D. in Artificial Intelligence/Knowledge Representation and is an active thought leader in the KG and AI space