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Building Knowledge Graphs in 10 Steps

Ontotext·
5 min read

Based on Ontotext's video on YouTube. If you like this content, support the original creators by watching, liking and subscribing to their content.

TL;DR

Start by translating business goals into explicit expert questions and requirements for domain scope, provenance, and maintenance.

Briefing

Building knowledge graphs in 10 steps starts with a simple premise: the graph’s value depends on nailing the business goal and the expert questions the data must answer. That means clarifying scope early—what decisions or analyses the organization wants—and then translating those needs into requirements for domain coverage, data provenance, and ongoing maintenance.

From there, the work shifts to sourcing and readiness. Relevant datasets, taxonomies, and other supporting information—whether proprietary, open, or commercially available—are gathered and analyzed to determine what can realistically feed the graph. Data quality becomes a gating factor: cleaning removes invalid or meaningless entries, fixes inconsistencies, and adjusts fields so the model can handle multiple values without breaking downstream logic.

The next phase is designing how meaning will be represented. A semantic data model is created by comparing existing schemas and planning how they will be harmonized. The process often involves engineering or reusing ontologies and application profiles, then formalizing the model using standards such as RDF Schema and OWL so the graph can be validated and reasoned over.

Integration follows, typically through ETL or data virtualization. ETL converts source data into RDF, while virtualization can expose data through mechanisms like OBDA, GraphQL federation, or similar approaches—paired with semantic metadata so updates and reuse are easier. Once data is in place, harmonization tackles the hardest reality of knowledge graphs: the same real-world entity appears in multiple datasets under different descriptions and taxonomies. Reconciliation, fusion, and alignment match entities across sources, merge attributes, and map differing classification systems.

After the graph is unified, it needs an operational layer. The architecture merges graphs using the RDF data model and relies on a graph database (e.g., a locally stored RDF store) to enforce semantics through reasoning, consistency checking, and validation. Scaling and performance are addressed by synchronizing with search engines such as Elasticsearch, aligning the system with anticipated usage.

The graph then becomes more than a container for existing facts. Reasoning, analytics, and text analysis augment it by extracting new entities and relationships from unstructured text, using inference and graph analytics to reveal patterns that weren’t explicitly present in any single source. The result is a graph that is more interconnected than the sum of its parts, enabling deeper analytics.

Finally, usability and lifecycle management close the loop. Knowledge discovery tools—SPARQL-like “Sparkle” queries, GraphQL interfaces, semantic search, faceted search, and data visualization—deliver answers to the original questions. Fairness principles ensure the data is findable, accessible, interoperable, and reusable. Maintenance procedures keep the graph live as sources evolve, preserving data quality while updates flow into enterprise knowledge graphs for unified data access and cognitive analytics.

Cornell Notes

A knowledge graph succeeds when it starts from clear business and expert questions, then builds a semantic model that can represent meaning consistently. The process moves from sourcing and cleaning data, to designing an RDF/OWL-based model, to integrating data via ETL or virtualization with semantic metadata. Harmonization reconciles duplicate entities and aligns attributes and taxonomies across datasets. An operational layer uses reasoning, validation, and search integration for performance and correctness. Finally, reasoning and text analysis enrich the graph, and knowledge discovery tools plus maintenance procedures ensure the graph remains usable and evolves over time.

Why does step one—clarifying business and expert requirements—determine whether the graph delivers value?

The graph is built to answer specific questions, so the goal behind collecting data must be defined first. That includes deciding what domain scope the graph should cover and what provenance and maintenance expectations exist. Without those constraints, later choices—data selection, ontology design, and query interfaces—risk producing a graph that is technically correct but doesn’t support the decisions or analyses the organization actually needs.

What does “clean data” mean in practice for knowledge graph construction?

Cleaning targets data quality issues that would otherwise propagate into the semantic layer. It includes removing invalid or meaningless entries, adjusting data fields to accommodate multiple values, and fixing inconsistencies. The goal is to make the data most applicable to the intended task, so downstream harmonization, reasoning, and search don’t break on malformed or contradictory inputs.

How do RDF Schema and OWL fit into the semantic data model step?

The semantic data model formalizes how entities and relationships should be represented and constrained. After analyzing existing schemata and planning harmonization, the model is formalized using standards like RDF Schema and OWL. That formalization enables validation and reasoning, which later supports consistency checking and inference-based enrichment.

What problem does reconciliation/fusion/alignment solve during harmonization?

Different datasets often describe the same real-world entity using different identifiers, labels, and taxonomies. Harmonization matches descriptions of “one in the same entity” across datasets with overlapping scope, merges attributes, and maps different taxonomies. This reduces duplication and improves the graph’s interconnectedness, which is essential for deeper analytics.

How does the architecture ensure semantics and performance once multiple graphs are merged?

A graph database based on the RDF data model can enforce semantics through reasoning, consistency checking, and validation. For scale and usability, it can run in a cluster and synchronize with search engines like Elasticsearch. That combination supports both correctness (semantic enforcement) and performance (fast retrieval aligned with usage patterns).

How does a knowledge graph become “more than the sum of its constituent datasets”?

Reasoning, analytics, and text analysis augment the graph by extracting new entities and relationships from text and applying inference and graph analytics. Instead of only storing existing facts, the system derives additional structure and connections, making the graph better interconnected and enabling deeper analytics than any single source could support.

Review Questions

  1. What specific activities occur between data cleaning and semantic model formalization, and why are RDF Schema/OWL important for later reasoning?
  2. Describe how harmonization handles duplicate entities across datasets and what kinds of mismatches it must resolve.
  3. Which components deliver end-user usability, and what maintenance steps keep the graph accurate as sources change?

Key Points

  1. 1

    Start by translating business goals into explicit expert questions and requirements for domain scope, provenance, and maintenance.

  2. 2

    Select datasets and taxonomies (open, proprietary, or commercial) based on how well they support the defined questions.

  3. 3

    Treat data cleaning as a prerequisite: remove invalid entries, fix inconsistencies, and normalize fields to support multi-value data.

  4. 4

    Build a semantic data model using standards like RDF Schema and OWL so the graph can be validated and reasoned over.

  5. 5

    Integrate sources via ETL to RDF or via data virtualization (e.g., OBDA, GraphQL federation) while generating semantic metadata for update and reuse.

  6. 6

    Harmonize overlapping datasets by reconciling entities, fusing attributes, and aligning taxonomies to eliminate duplicates and contradictions.

  7. 7

    Keep the graph usable and trustworthy through reasoning/text enrichment, query and search interfaces, and ongoing maintenance procedures.

Highlights

The graph’s usefulness is driven by step one: the business goal and the exact questions the data must answer.
Harmonization is where most real-world complexity lives—matching the same entity across datasets and mapping differing taxonomies.
Reasoning plus text analysis turns stored data into derived knowledge by extracting new entities/relationships and applying inference.
Operational success depends on an architecture that enforces semantics (reasoning/validation) and scales retrieval by syncing with search engines like Elasticsearch.

Topics

  • Knowledge Graphs
  • Semantic Data Modeling
  • RDF and OWL
  • Data Harmonization
  • Graph Reasoning

Mentioned

  • ETL
  • RDF
  • OWL
  • OBDA