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curl -X GET "https://api.omophub.com/v1/relationships/types?include_usage_stats=true&include_examples=true&category=hierarchical" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json"

{
  "success": true,
  "data": {
    "relationship_types": [
    {
      "relationship_id": "116680003",
      "relationship_name": "Is a",
      "reverse_relationship_name": "Subsumes",
      "relationship_concept_id": 116680003,
      "category": "hierarchical",
      "definition": "The source concept is a subtype or instance of the destination concept",
      "description": "Represents the primary hierarchical relationship in SNOMED CT, defining subsumption between concepts",
      "is_hierarchical": true,
      "is_defining": true,
      "is_symmetric": false,
      "is_transitive": true,
      "primary_vocabularies": ["SNOMED", "LOINC"],
      "domain_restrictions": [],
      "usage_statistics": {
        "total_relationships": 1247890,
        "unique_concepts_as_subject": 432156,
        "unique_concepts_as_object": 298745,
        "most_common_domains": ["Condition", "Procedure", "Substance"],
        "average_per_concept": 2.9,
        "popularity_rank": 1
      },
      "examples": [
        {
          "subject_concept_id": 44054006,
          "subject_concept_name": "Type 2 diabetes mellitus", 
          "object_concept_id": 73211009,
          "object_concept_name": "Diabetes mellitus",
          "vocabulary_id": "SNOMED",
          "example_description": "Type 2 diabetes is a specific type of diabetes mellitus"
        },
        {
          "subject_concept_id": 386053000,
          "subject_concept_name": "Evaluation procedure",
          "object_concept_id": 71388002,
          "object_concept_name": "Procedure",
          "vocabulary_id": "SNOMED",
          "example_description": "Evaluation procedures are a subtype of general procedures"
        }
      ],
      "valid_start_date": "1970-01-01T00:00:00Z",
      "valid_end_date": "2099-12-31T00:00:00Z",
      "created_date": "1970-01-01T00:00:00Z"
    },
    {
      "relationship_id": "123005000",
      "relationship_name": "Part of",
      "reverse_relationship_name": "Has part",
      "relationship_concept_id": 123005000,
      "category": "part_whole",
      "definition": "The source concept is a part, component, or constituent of the destination concept",
      "description": "Represents part-whole relationships, commonly used for anatomical structures and complex procedures",
      "is_hierarchical": false,
      "is_defining": true,
      "is_symmetric": false,
      "is_transitive": true,
      "primary_vocabularies": ["SNOMED"],
      "domain_restrictions": ["Procedure", "Device", "Spec Anatomic Site"],
      "usage_statistics": {
        "total_relationships": 89456,
        "unique_concepts_as_subject": 34521,
        "unique_concepts_as_object": 18234,
        "most_common_domains": ["Spec Anatomic Site", "Procedure"],
        "average_per_concept": 2.6,
        "popularity_rank": 5
      },
      "examples": [
        {
          "subject_concept_id": 7771000,
          "subject_concept_name": "Left ventricular structure",
          "object_concept_id": 80891009,
          "object_concept_name": "Heart structure",
          "vocabulary_id": "SNOMED",
          "example_description": "Left ventricle is part of the heart structure"
        }
      ],
      "valid_start_date": "1970-01-01T00:00:00Z",
      "valid_end_date": "2099-12-31T00:00:00Z",
      "created_date": "2002-01-31T00:00:00Z"
    },
    {
      "relationship_id": "maps_to",
      "relationship_name": "Maps to",
      "reverse_relationship_name": "Mapped from",
      "relationship_concept_id": 44819096,
      "category": "mapping",
      "definition": "The source concept from one vocabulary corresponds to the destination concept in another vocabulary",
      "description": "Cross-vocabulary mapping relationship used to link equivalent or similar concepts across different terminologies",
      "is_hierarchical": false,
      "is_defining": false,
      "is_symmetric": false,
      "is_transitive": false,
      "primary_vocabularies": ["SNOMED", "ICD10CM", "ICD10", "RxNorm"],
      "usage_statistics": {
        "total_relationships": 567234,
        "unique_concepts_as_subject": 245678,
        "unique_concepts_as_object": 198432,
        "most_common_domains": ["Condition", "Drug", "Procedure"],
        "average_per_concept": 2.3,
        "popularity_rank": 2
      },
      "examples": [
        {
          "subject_concept_id": 201826,
          "subject_concept_name": "Type 2 diabetes mellitus",
          "object_concept_id": 45757292,
          "object_concept_name": "Type 2 diabetes mellitus",
          "vocabulary_id": "ICD10CM",
          "example_description": "SNOMED concept maps to equivalent ICD-10-CM concept"
        }
      ],
      "valid_start_date": "2010-01-01T00:00:00Z",
      "valid_end_date": "2099-12-31T00:00:00Z",
      "created_date": "2010-01-01T00:00:00Z"
    }
    ],
    "relationship_categories": {
      "hierarchical": 2,
      "associative": 15,
      "mapping": 8,
      "part_whole": 4,
      "temporal": 6,
      "spatial": 3,
      "causative": 2,
      "other": 12
    },
    "vocabulary_distribution": {
      "SNOMED": 28,
      "RxNorm": 8,
      "ICD10CM": 3,
      "LOINC": 5,
      "HCPCS": 2
    }
  },
  "meta": {
    "pagination": {
      "page": 1,
      "page_size": 100,
      "total_items": 52,
      "total_pages": 1,
      "has_next": false,
      "has_previous": false
    },
    "request_id": "req_relationship_types_67891234",
    "timestamp": "2024-12-22T10:30:00Z",
    "vocab_release": "2025.2"
  }
}
This endpoint provides comprehensive information about all relationship types available in the medical vocabularies, helping users understand how concepts are connected and which relationship types are available for queries and analysis.

​
Query Parameters

​
vocabulary_ids
string
Filter relationship types to specific vocabularies
Example: SNOMED,RxNorm,ICD10CM
​
include_reverse
boolean
default:"true"
Include reverse relationship names and definitions
​
include_usage_stats
boolean
default:"false"
Include usage statistics for each relationship type
​
include_examples
boolean
default:"false"
Include example concept pairs for each relationship type
​
category
string
Filter by relationship category
Options: hierarchical, associative, mapping, part_whole, temporal, spatial, causative, other
​
is_defining
boolean
Filter by whether relationships are defining/essential for concepts
​
standard_only
boolean
default:"true"
Only return relationship types used with standard concepts
​
page_size
integer
default:"100"
Number of relationship types to return per page (max 500)
​
page
integer
default:"1"
Page number for pagination (1-based)

​
Response

​
relationship_types
array
Array of available relationship types with their properties
​
relationship_categories
object
Summary of relationship types by category
​
vocabulary_distribution
object
Distribution of relationship types by vocabulary
​
meta
object
Response metadata and pagination information
curl -X GET "https://api.omophub.com/v1/relationships/types?include_usage_stats=true&include_examples=true&category=hierarchical" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json"

{
  "success": true,
  "data": {
    "relationship_types": [
    {
      "relationship_id": "116680003",
      "relationship_name": "Is a",
      "reverse_relationship_name": "Subsumes",
      "relationship_concept_id": 116680003,
      "category": "hierarchical",
      "definition": "The source concept is a subtype or instance of the destination concept",
      "description": "Represents the primary hierarchical relationship in SNOMED CT, defining subsumption between concepts",
      "is_hierarchical": true,
      "is_defining": true,
      "is_symmetric": false,
      "is_transitive": true,
      "primary_vocabularies": ["SNOMED", "LOINC"],
      "domain_restrictions": [],
      "usage_statistics": {
        "total_relationships": 1247890,
        "unique_concepts_as_subject": 432156,
        "unique_concepts_as_object": 298745,
        "most_common_domains": ["Condition", "Procedure", "Substance"],
        "average_per_concept": 2.9,
        "popularity_rank": 1
      },
      "examples": [
        {
          "subject_concept_id": 44054006,
          "subject_concept_name": "Type 2 diabetes mellitus", 
          "object_concept_id": 73211009,
          "object_concept_name": "Diabetes mellitus",
          "vocabulary_id": "SNOMED",
          "example_description": "Type 2 diabetes is a specific type of diabetes mellitus"
        },
        {
          "subject_concept_id": 386053000,
          "subject_concept_name": "Evaluation procedure",
          "object_concept_id": 71388002,
          "object_concept_name": "Procedure",
          "vocabulary_id": "SNOMED",
          "example_description": "Evaluation procedures are a subtype of general procedures"
        }
      ],
      "valid_start_date": "1970-01-01T00:00:00Z",
      "valid_end_date": "2099-12-31T00:00:00Z",
      "created_date": "1970-01-01T00:00:00Z"
    },
    {
      "relationship_id": "123005000",
      "relationship_name": "Part of",
      "reverse_relationship_name": "Has part",
      "relationship_concept_id": 123005000,
      "category": "part_whole",
      "definition": "The source concept is a part, component, or constituent of the destination concept",
      "description": "Represents part-whole relationships, commonly used for anatomical structures and complex procedures",
      "is_hierarchical": false,
      "is_defining": true,
      "is_symmetric": false,
      "is_transitive": true,
      "primary_vocabularies": ["SNOMED"],
      "domain_restrictions": ["Procedure", "Device", "Spec Anatomic Site"],
      "usage_statistics": {
        "total_relationships": 89456,
        "unique_concepts_as_subject": 34521,
        "unique_concepts_as_object": 18234,
        "most_common_domains": ["Spec Anatomic Site", "Procedure"],
        "average_per_concept": 2.6,
        "popularity_rank": 5
      },
      "examples": [
        {
          "subject_concept_id": 7771000,
          "subject_concept_name": "Left ventricular structure",
          "object_concept_id": 80891009,
          "object_concept_name": "Heart structure",
          "vocabulary_id": "SNOMED",
          "example_description": "Left ventricle is part of the heart structure"
        }
      ],
      "valid_start_date": "1970-01-01T00:00:00Z",
      "valid_end_date": "2099-12-31T00:00:00Z",
      "created_date": "2002-01-31T00:00:00Z"
    },
    {
      "relationship_id": "maps_to",
      "relationship_name": "Maps to",
      "reverse_relationship_name": "Mapped from",
      "relationship_concept_id": 44819096,
      "category": "mapping",
      "definition": "The source concept from one vocabulary corresponds to the destination concept in another vocabulary",
      "description": "Cross-vocabulary mapping relationship used to link equivalent or similar concepts across different terminologies",
      "is_hierarchical": false,
      "is_defining": false,
      "is_symmetric": false,
      "is_transitive": false,
      "primary_vocabularies": ["SNOMED", "ICD10CM", "ICD10", "RxNorm"],
      "usage_statistics": {
        "total_relationships": 567234,
        "unique_concepts_as_subject": 245678,
        "unique_concepts_as_object": 198432,
        "most_common_domains": ["Condition", "Drug", "Procedure"],
        "average_per_concept": 2.3,
        "popularity_rank": 2
      },
      "examples": [
        {
          "subject_concept_id": 201826,
          "subject_concept_name": "Type 2 diabetes mellitus",
          "object_concept_id": 45757292,
          "object_concept_name": "Type 2 diabetes mellitus",
          "vocabulary_id": "ICD10CM",
          "example_description": "SNOMED concept maps to equivalent ICD-10-CM concept"
        }
      ],
      "valid_start_date": "2010-01-01T00:00:00Z",
      "valid_end_date": "2099-12-31T00:00:00Z",
      "created_date": "2010-01-01T00:00:00Z"
    }
    ],
    "relationship_categories": {
      "hierarchical": 2,
      "associative": 15,
      "mapping": 8,
      "part_whole": 4,
      "temporal": 6,
      "spatial": 3,
      "causative": 2,
      "other": 12
    },
    "vocabulary_distribution": {
      "SNOMED": 28,
      "RxNorm": 8,
      "ICD10CM": 3,
      "LOINC": 5,
      "HCPCS": 2
    }
  },
  "meta": {
    "pagination": {
      "page": 1,
      "page_size": 100,
      "total_items": 52,
      "total_pages": 1,
      "has_next": false,
      "has_previous": false
    },
    "request_id": "req_relationship_types_67891234",
    "timestamp": "2024-12-22T10:30:00Z",
    "vocab_release": "2025.2"
  }
}

​
Usage Examples

​
All Relationship Types

Get all available relationship types: 
const allTypes = await fetch('/v1/relationships/types');

​
Hierarchical Relationships Only

Get relationship types that create hierarchies: 
const hierarchical = await fetch('/v1/relationships/types?category=hierarchical&include_examples=true');

​
SNOMED Relationship Types

Get relationship types used in SNOMED CT: 
const snomedTypes = await fetch('/v1/relationships/types?vocabulary_ids=SNOMED&include_usage_stats=true');

​
Mapping Relationship Types

Find relationship types used for cross-vocabulary mapping: 
const mappingTypes = await fetch('/v1/relationships/types?category=mapping&include_examples=true');

​
Defining Relationships

Get relationship types that are defining for concepts: 
const defining = await fetch('/v1/relationships/types?is_defining=true&include_usage_stats=true');

​
Notes

  • Relationship types define the semantic connections between medical concepts
  • Hierarchical relationships (like “Is a”) create taxonomic structures essential for classification
  • Defining relationships are crucial for concept definition and meaning
  • Symmetric relationships work in both directions (A relates to B implies B relates to A)
  • Transitive relationships can be chained (A→B, B→C implies A→C)
  • Cross-vocabulary mappings use specialized relationship types like “Maps to”
  • Usage statistics help identify the most important and commonly used relationship types
  • Some relationship types may be restricted to specific domains or vocabularies
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