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Graph SHACL Validation

Date: 2026-04-15

Purpose

Markdown-LD Knowledge Bank validates built RDF graphs with SHACL so callers can detect malformed graph construction through a standards-based report instead of custom post-processing.

The feature uses dotNetRdf.Shacl over the in-memory KnowledgeGraph. It does not add a server, database, cache, provider SDK, or Python runtime.

Flow

flowchart LR
    Markdown["Markdown documents"] --> Pipeline["MarkdownKnowledgePipeline"]
    Pipeline --> Facts["Merged entities and assertions"]
    Facts --> Reification["Direct RDF edges plus rdf:Statement metadata"]
    Reification --> Graph["KnowledgeGraph"]
    Shapes["Default or caller SHACL shapes"] --> Validator["dotNetRDF ShapesGraph"]
    Graph --> Validator
    Validator --> Report["KnowledgeGraphShaclValidationReport"]
    Report --> Caller["Caller"]
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Default Shapes

The built-in shapes graph validates:

  • schema:Article nodes have schema:name and IRI provenance.
  • common entity classes have schema:name.
  • schema:sameAs values are IRIs.
  • prov:wasDerivedFrom values are IRIs.
  • reified rdf:Statement assertion metadata has one IRI subject, predicate, object, and a decimal kb:confidence from 0 through 1.

Callers can pass custom Turtle SHACL shapes to KnowledgeGraph.ValidateShacl(shapesTurtle) or MarkdownKnowledgeBuildResult.ValidateShacl(shapesTurtle).

Assertion Metadata

Graph assertions remain direct RDF edges for existing SPARQL/search callers. Each assertion also receives RDF reification metadata:

flowchart TB
    Subject["subject IRI"] -->|"direct predicate"| Object["object IRI"]
    Statement["blank rdf:Statement"] -->|"rdf:subject"| Subject
    Statement -->|"rdf:predicate"| Predicate["predicate IRI"]
    Statement -->|"rdf:object"| Object
    Statement -->|"kb:confidence"| Confidence["xsd:decimal"]
    Statement -->|"prov:wasDerivedFrom"| Source["source IRI or invalid literal"]
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Invalid caller-authored sameAs and provenance values are represented as literals so SHACL can report node-kind violations instead of silently dropping them.

Testing Methodology

Flow tests cover:

  • valid Markdown and configured graph rules conform to the default shapes;
  • invalid schema:sameAs, provenance, and assertion confidence produce SHACL results;
  • caller-supplied shapes validate the same built graph;
  • sameAs-first entity merge rewrites assertion endpoints before validation.

Verification commands:

  • dotnet build MarkdownLd.Kb.slnx --no-restore
  • dotnet test --solution MarkdownLd.Kb.slnx --configuration Release
  • dotnet format MarkdownLd.Kb.slnx --verify-no-changes
  • coverage command from the root AGENTS.md