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Relationship Specification

Part of: RDF Specification

This document specifies how RDF glossary term relationships are extracted, converted, and mapped to DataHub relationship entities.

Overview​

Glossary term relationships represent semantic connections between business terms. This entity type specifically handles term-to-term relationships extracted from SKOS properties.

Important: This entity only extracts skos:broader and skos:narrower relationships. Other SKOS properties (skos:related, skos:exactMatch, skos:closeMatch) are not extracted by this entity.

RDF Source Patterns​

Supported Relationships​

Only these SKOS properties are extracted:

  1. skos:broader - Child term points to parent term (more general concept)
  2. skos:narrower - Parent term points to child term (more specific concept)

Example:

accounts:Customer_ID a skos:Concept ;
    skos:prefLabel "Customer Identifier" ;
    skos:broader accounts:Customer_Data .

accounts:Customer_Data a skos:Concept ;
    skos:prefLabel "Customer Data" ;
    skos:narrower accounts:Customer_ID ;
    skos:narrower accounts:Customer_Name .

Unsupported Relationships​

These SKOS properties are not extracted by the relationship entity:

  • skos:related - Associative relationships (not supported)
  • skos:exactMatch - Reserved for field-to-term mappings only
  • skos:closeMatch - Similar concepts (not supported)
  • skos:broadMatch - Broader match (not supported)
  • skos:narrowMatch - Narrower match (not supported)

Note: skos:exactMatch is handled separately for field-to-term mappings in dataset field definitions, not as term-to-term relationships.

Relationship Types​

The relationship entity defines these relationship types:

class RelationshipType(Enum):
    BROADER = "broader"      # skos:broader
    NARROWER = "narrower"    # skos:narrower

DataHub Mapping​

Relationship Mapping​

Term-to-term relationships are mapped to DataHub's isRelatedTerms relationship:

  • skos:broader (child → parent):

    • Source term (child) → isRelatedTerms → Target term (parent)
    • Creates bidirectional relationship: child inherits from parent

  • skos:narrower (parent → child):

    • Source term (parent) → isRelatedTerms → Target term (child)
    • Creates bidirectional relationship: parent contains child

DataHub Relationship:

  • Field: isRelatedTerms
  • UI Display: "Inherits" (for child) or "Contains" (for parent)
  • Semantic Meaning: Hierarchical term relationship

URN Generation​

Both source and target terms use glossary term URN generation:

  • Format: urn:li:glossaryTerm:({path_segments})
  • Uses GlossaryTermUrnGenerator for consistent URN creation

Extraction Process​

Bulk Extraction​

Relationships are extracted in bulk from the entire RDF graph:

  1. Find all skos:broader triples: (subject, skos:broader, object)
  2. Find all skos:narrower triples: (subject, skos:narrower, object)
  3. Deduplicate: Remove duplicate relationships
  4. Convert to RDFRelationship: Create RDFRelationship objects with source/target URIs

Per-Term Extraction​

Relationships can also be extracted for a specific term:

relationships = extractor.extract_for_term(graph, term_uri)

Returns all relationships where the specified term is the source.

DataHub Integration​

MCP Creation​

Relationships are converted to DataHub MCPs that create isRelatedTerms edges:

# RDF Relationship
RDFRelationship(
    source_uri="http://example.com/terms/Customer_ID",
    target_uri="http://example.com/terms/Customer_Data",
    relationship_type=RelationshipType.BROADER
)

# DataHub Relationship
DataHubRelationship(
    source_urn="urn:li:glossaryTerm:(terms,Customer_ID)",
    target_urn="urn:li:glossaryTerm:(terms,Customer_Data)",
    relationship_type="broader"
)

Bidirectional Relationships​

When a skos:broader relationship is created:

  • Child term gets isRelatedTerms pointing to parent (inherits)
  • Parent term gets hasRelatedTerms pointing to child (contains)

This bidirectional mapping is handled automatically by DataHub's relationship model.

Validation​

Relationship Validation​

  1. Source/Target Validation: Both source and target must be valid term URIs
  2. URN Generation: Both URIs must successfully convert to DataHub URNs
  3. Deduplication: Duplicate relationships (same source, target, type) are removed

Limitations​

  1. Only Hierarchical Relationships: Only skos:broader and skos:narrower are supported
  2. No Associative Relationships: skos:related and skos:closeMatch are not extracted
  3. No External References: skos:exactMatch is reserved for field-to-term mappings only
  4. Term-to-Term Only: This entity does not handle field-to-term relationships (handled by dataset entity)

Relationship to Glossary Term Entity​

The relationship entity is separate from the glossary term entity:

  • Glossary Term Entity: Extracts term definitions, properties, constraints
  • Relationship Entity: Extracts term-to-term relationships only

This separation allows relationships to be processed independently and enables selective export of relationships without full term processing.