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Domain Specification

Part of: RDF Specification

This document specifies how DataHub domains are constructed from entity IRI paths.

Overview​

Domains are not extracted from RDF graphs. Instead, they are constructed from the IRI path segments of glossary terms. Domains provide hierarchical organization for business entities.

Important: Domains are not registered entities (no ENTITY_METADATA). They are built by the DomainBuilder class from existing entities.

Domain Construction Logic​

Path Segment Extraction​

Domains are created from the parent path segments of entity IRIs:

  1. Extract IRI path: Parse entity IRI to get path segments
  2. Remove entity name: Exclude the last segment (entity name itself)
  3. Create domain hierarchy: Each parent segment becomes a domain level
  4. Assign entities: Entities are assigned to their immediate parent domain (leaf domain)

Example​

Entity IRI: https://bank.com/finance/accounts/customer_id

Path Segments: ['bank.com', 'finance', 'accounts', 'customer_id']

Parent Segments (for domain creation): ['bank.com', 'finance', 'accounts']

Domains Created:

  • bank.com (root domain)
  • finance (child of bank.com)
  • accounts (child of finance, leaf domain)

Entity Assignment: Term assigned to accounts domain (most specific parent)

Domain Hierarchy​

Domains form a hierarchical tree structure:

bank.com (root)
  └── finance
      └── accounts (leaf - contains entities)

Parent-Child Relationships​

  • Each domain has an optional parent_domain_urn
  • Root domains have no parent
  • Child domains reference their parent via parent_domain_urn

Domain Creation Rules​

Domains with Glossary Terms​

Rule: Domains that have glossary terms in their hierarchy are created.

  • Domains are created when they contain glossary terms
  • Domains provide hierarchical organization for business vocabulary

Entity Assignment​

Entities are assigned to their immediate parent domain (leaf domain):

  • Glossary Terms: Assigned to the domain corresponding to their parent path

Example:

  • Term: https://bank.com/finance/accounts/customer_id → Assigned to accounts domain

URN Generation​

Domain URNs are generated from path segments:

Format: urn:li:domain:({path_segments})

Example:

  • Path: ('bank.com', 'finance', 'accounts')
  • URN: urn:li:domain:(bank.com,finance,accounts)

Path Segment Tuple​

Path segments are represented as tuples:

  • ('bank.com',) - Root domain
  • ('bank.com', 'finance') - Second-level domain
  • ('bank.com', 'finance', 'accounts') - Third-level domain (leaf)

Domain Properties​

Required Properties​

  • URN: Generated from path segments
  • Name: Last segment of the path (e.g., "accounts")

Optional Properties​

  • Parent Domain URN: Reference to parent domain (if not root)
  • Description: Can be set from domain metadata if available
  • Glossary Terms: List of terms assigned to this domain

DataHub Integration​

Domain MCP Creation​

Domains are created via DataHub MCPs:

  1. Domain Properties MCP: Creates the domain entity with name, description
  2. Domain Hierarchy MCP: Establishes parent-child relationships
  3. Domain Hierarchy MCP: Establishes parent-child relationships

Example​

Input Entities:

  • Term: https://bank.com/finance/accounts/customer_id

Domains Created:

DataHubDomain(
    urn="urn:li:domain:(bank.com,finance,accounts)",
    name="accounts",
    parent_domain_urn="urn:li:domain:(bank.com,finance)",
    glossary_terms=[...],  # customer_id term
)

DataHubDomain(
    urn="urn:li:domain:(bank.com,finance)",
    name="finance",
    parent_domain_urn="urn:li:domain:(bank.com)",
    glossary_terms=[],
)

DataHubDomain(
    urn="urn:li:domain:(bank.com)",
    name="bank.com",
    parent_domain_urn=None,  # Root domain
    glossary_terms=[],
)

Limitations​

  1. No RDF Extraction: Domains are not extracted from RDF - they are constructed
  2. Glossary Term Requirement: Domains without glossary terms are not created
  3. Path-Based Only: Domain structure is derived solely from IRI paths
  4. No Explicit Domain Definitions: RDF does not contain explicit domain definitions - they are inferred

Relationship to Other Entities​

  • Glossary Terms: Provide path segments for domain construction and determine which domains are created