Jonatan Matajonmatum.com
conceptsnotesexperimentsessays
© 2026 Jonatan Mata. All rights reserved.v2.1.1
Concepts

Knowledge Graphs

Data structures representing knowledge as networks of entities and relationships, enabling reasoning, connection discovery, and semantic queries over complex domains.

seed#knowledge-graph#graph#ontology#relationships#semantic-web#linked-data

What it is

A knowledge graph is a structure that represents information as a network of entities (nodes) connected by relationships (edges). Unlike a tabular database, a graph naturally captures connections between concepts, enabling discovery of implicit relationships and reasoning over complex domains.

This site uses a knowledge graph: each concept is a node, and relationships between concepts are edges forming a navigable network.

Basic structure

(Entity) --[Relationship]--> (Entity)

(Git) --[is base of]--> (GitHub)
(GitHub) --[has feature]--> (GitHub Actions)
(GitHub Actions) --[implements]--> (CI/CD)

Triples

The fundamental unit is the triple: subject → predicate → object.

(LLM) --[uses]--> (Transformer)
(RAG) --[reduces]--> (Hallucinations)
(MCP) --[standardizes]--> (Tool Use)

Types of knowledge graphs

  • Taxonomic: classification hierarchies (is-a, part-of)
  • Semantic: rich relationships with defined types (ontologies)
  • Property graphs: nodes and edges with arbitrary properties
  • RDF: W3C standard for linked data on the web

Applications with AI

GraphRAG

Combining knowledge graphs with RAG:

  • Navigate relationships to find relevant context
  • Answer questions requiring connecting multiple facts
  • Better than vector RAG for relationship questions

Grounding

Using the graph as a source of truth to reduce hallucinations.

Discovery

Finding non-obvious connections between concepts — exactly what this site's /graph page does.

Tools

ToolType
Neo4jGraph database
Amazon NeptuneManaged graph on AWS
NetworkXPython graph library
D3.js / vis.jsGraph visualization

Why it matters

Knowledge graphs represent information as entities and relationships, enabling the discovery of connections that are not evident in tabular data. They are the foundation of recommendation systems, semantic search, and knowledge bases like the one powering this site.

References

  • Knowledge Graphs — Hogan et al., 2021. Comprehensive survey.
  • From Local to Global: A Graph RAG Approach — Microsoft Research, 2024.
  • Neo4j Graph Database — Neo4j, 2024. Introduction to graph databases.

Related content

  • Semantic Search

    Information retrieval technique that uses vector embeddings to find results by meaning, not just exact keyword matching.

  • Artificial Intelligence

    Field of computer science dedicated to creating systems capable of performing tasks that normally require human intelligence, from reasoning and perception to language generation.

  • From Prototype to Production: A Serverless Second Brain on AWS

    Architecture design for scaling a personal second brain to a production system with AWS serverless — from the current prototype to specialized use cases in legal, research, and community building.

  • Building a Second Brain in Public

    Chronicle of building a second brain with a knowledge graph, bilingual pipeline, and agent endpoints — in days, not weeks, and what that teaches about the gap between theory and working systems.

  • Serverless Second Brain

    Production-ready serverless backend for a personal knowledge graph — DynamoDB, Lambda, Bedrock, MCP, Step Functions. The implementation of the architecture described in the 'From Prototype to Production' essay.

Concepts