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