AI GLOSSARY
Knowledge Graph
A knowledge graph connects entities and their relationships to form a structured knowledge model. From Google Search to corporate knowledge—knowledge graphs are the foundation of many intelligent systems. When combined with LLMs, they give rise to particularly powerful applications.
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Building Blocks
Entities, Relationships, Attributes, Ontology
Benefits
Reasoning, Explainability, Consistency, Search
Applications
Search, Recommendations, Compliance, Analysis
Best Practices
for powerful knowledge graphs
Why Knowledge Graphs Have Become Important
LLMs are powerful, but they can hallucinate. Knowledge graphs provide structured, verifiable knowledge—for reliable answers. The combination of the two is one of the most important trends in productive AI for 2026.
Structured Knowledge
Facts and relationships are explicit—the model doesn't have to guess.
Explainability
Answers can be traced back to specific graph nodes.
Reasoning Possible
Multiple chained inferences—not just direct facts.
Fewer Hallucinations
LLM plus Graph = Fact-based answers.
Ensuring Consistency
Changes in the graph propagate—knowledge remains coherent.
Domain-Specific
Structured representation of corporate knowledge — more powerful than RAG alone.
What is a knowledge graph?
A knowledge graph is a data structure that represents entities (people, products, places, concepts) and their relationships as a network. Instead of rows in tables: nodes and edges with semantic information. Example: 'Berlin' (node) 'is the capital of' (edge) 'Germany' (node).
Core components: entities (things, people, concepts), relationships (categorized connections—'works at,' 'is part of'), attributes (properties per node), ontology (schema with permitted types and relationships), rules (constraints and inference logic).
Well-known knowledge graphs: Google Knowledge Graph (behind Google Search), Wikidata (open, collaboratively maintained database), DBpedia (structured data from Wikipedia), enterprise knowledge graphs (internal corporate graphs at large companies), domain-specific graphs (medicine, chemistry, law).
Knowledge graphs are becoming increasingly interesting for small and medium-sized businesses—especially when combined with LLMs. Where structured knowledge is important (compliance, product relationships, customer networks), graphs provide significantly more precise answers than RAG alone. Setting them up is more complex, but the long-term benefits are significant.
Knowledge Graph Techniques in Detail
These eight techniques form the backbone of modern knowledge graphs:
Ontology Engineering
Entity Extraction
Entity Resolution
Graph Databases
SPARQL / Cypher
Graph Embeddings
Reasoning Engines
Graph-RAG
Best Practices for Knowledge Graphs
These six principles have proven effective:
- Start small: One department, a few entity types—then expand.
- Buildthe ontology iteratively: Don’t plan for perfection—learn and adapt through practice.
- Ensure data quality: Incorrect facts in the graph propagate—build in quality assurance processes.
- Combine with LLMs: Graph-RAG is significantly more powerful than pure RAG or a pure graph.
- Early governance: Regulate maintenance, approvals, and changes in a structured way.
- Demonstrate business value: Show concrete applications, not just diagrams.
Type 1
Public Graphs
Wikidata, DBpedia. Foundational—but not company-specific.
Public
Type 2
Enterprise Graph
Company graphs with ERP, CRM, and products. Maximum business value.
Companies
Type 3
Domain Graph
Specializes in the following fields: medicine, law, and chemistry.
Technical
Common Mistakes in Knowledge Graphs
We often see these pitfalls:
- An overly ambitious ontology: Trying to model everything perfectly—the project gets bogged down in details.
- No business case: Graph built, but no one uses it—an expensive art installation.
- Data quality ignored: Automatically extracted facts without QA—the graph quickly becomes error-prone.
- No maintenance process: The graph becomes outdated—irrelevant after just a few months.
- No LLM integration: A graph on its own without AI applications—wastes potential.
Knowledge Graph vs. RAG vs. Database
A comparison of three knowledge structures:
- Knowledge graph: Interconnected facts with semantics. Ideal for reasoning and explainability.
- RAG: Similarity-based text search. Quick to set up, but lacks true structure.
- Database: Tables with fixed fields. For transactions—not for knowledge networks.
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Frequently Asked Questions About Knowledge Graphs
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When is a knowledge graph worth it?
When relationships between entities are important (networks, hierarchies, contracts). For compliance, recommendations, and complex analyses.
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What is Graph-RAG?
Combination of a knowledge graph and an LLM — The LLM uses structured graph knowledge instead of just text snippets. Significantly more accurate than RAG alone.
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Which databases are standard?
Neo4j (market leader), TigerGraph, Amazon Neptune, Stardog. For smaller setups: RDF stores or property graph databases.
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What is SPARQL?
A query language for RDF-based knowledge graphs—similar to SQL for databases. Cypher is the alternative for property graphs (Neo4j).
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How much does it cost?
Setup: 50,000–300,000 EUR, depending on scope. Ongoing operations: 5,000–30,000 EUR per month. ROI is typically achieved starting in the second year.
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How is the Knowledge Graph related to RAG?
RAG leverages text similarity. Graph-RAG supplements structured knowledge—for reliable, explainable answers.
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Are knowledge graphs obsolete because of LLMs?
No, on the contrary. Knowledge graphs compensate for LLM weaknesses (hallucinations). Combining the two is more powerful than either technique alone.
Build Knowledge Graphs with prodot
In a free initial consultation, we’ll identify your most important knowledge network and outline a knowledge graph pilot—complete with a clear business case.
As an AI partner for small and medium-sized businesses, we build knowledge graphs in a practical way—using ontology, data integration, graph databases, and LLM integration.
What We Offer
- AI Consulting — Knowledge Graph Design and Implementation.
- RAG in the Glossary — the related retrieval technique.
- Data governance —the foundation for clean graphs.
- Semantic search — a complementary technology.