SNOMEDCore StructuresSNOMEDCore Structures2nd AAHA Software Vendors Summit – April 21, 2009

Terminology of TerminologyTerminology of Terminology• Concept

• embodiment of a particular meaning• Really a “virtual” element in the system• The string in concepts table is a member of the related list of

descriptions.• Description

• Any string used to represent a concept• Relationship

• (in SNOMED) an object – attribute – value triple connecting two concepts through an attribute

• Relationships in SNOMED are explicit rather than implicit (as was the case in SNOMED III)

Terminology of TerminologyTerminology of Terminology• Extension (valid)

• SNOMED content outside of SNOMED core but integrated such that it can be queried as if it were part of SNOMED core.

• An official extension is created by an organization that holds a namespace identifier (more later).

• Subset• A functional subset of SNOMED is a list of concepts extracted

from core, an extension or both to serve a defined purpose.• Navigational subset

• A SNOMED subset that includes adequate hierarchical information to allow navigation (browsing).

SNOMED CoreSNOMED Core

• Concepts Table• Each row in this table represents a medical concept.

• Descriptions Table• Each row in this table specifies a term that can be applied to describe a single

clinical concept.• Relationships Table

• Each row in this table specifies a relationship between two clinical concepts. The nature of each relationship is represented using a special kind of clinical concept.

SNOMED CoreSNOMED Core

• A concept is described by the term (string) in 2-n descriptions• At least the Fully Specified Name (FSN) + Preferred

Term

• Each description refers to (only) 1 concept.

SNOMED CoreSNOMED Core

• A concept is the source of 1-n relationships (except the root concept).

• A concept is the target of 1-n relationships.• A concept represents the type of relationship.• A relationship refers to 3 concepts: a source, a target,

and a relationship type.

Concepts Table FieldsConcepts Table FieldsKey Fields

ConceptId The unique SNOMED Clinical Terms Identifier for this Concept.

Data Fields

ConceptStatus The status of a Concept indicates whether it is in active use and, if not, indicates the reason for withdrawal from current use.

FullySpecifiedName A unique phrase that describes a Concept in a way that is intended to be unambiguous.

CTV3ID The Read Code for this Concept.

SNOMEDID The current SNOMED identifier for this Concept.

IsPrimitive Indicates whether a Concept is Primitive or Fully defined by its current set of Defining characteristics.

Descriptions TableDescriptions TableKey Fields

DescriptionId The unique SNOMED CT Identifier for this Description.

Data Fields

DescriptionStatus The status of a Description indicates whether it is in active use and, if not, indicates the reason for withdrawal from current use.

ConceptId The unique SNOMED CT Identifier of the associated Concept. (Foreign key to Concepts Table).

Term The text of a Term used to describe the associated Concept.

InitialCapitalStatus An indication of whether the capitalization status of the first character of the Term is significant.

DescriptionType An indication of whether the Term is the Fully Specified Name, Preferred Term or Synonym for the Concept to which this Description applies.

LanguageCode An indication of a Language or Dialect in which this Description is valid. The language or dialect subset ultimately defines the descriptions for each concept.

Concepts -> DescriptionsConcepts -> Descriptions

233604007 D2-0007F Pneumonia (concept)

2Synonym In Local Extension233604007xxxxxxzzz11x

2Synonym in NAHLN Extension233604007xxxxxxyyy11x

2Synonym in Core233604007xxxxxx01x

1Pneumonia233604007621810017

3Pneumonia (Disorder)233604007350049016

1 = “preferred” description (term) – preferred by SNOMED, perhaps not your users2 = synonym (alternate)3 = fully specified name

Component History Table (future use)Component History Table (future use)

Key FieldsKey Fields

ComponentIDComponentID The unique SNOMED CT Identifier for the changed Component.

ReleaseVersionReleaseVersion The version of SNOMED CT in which this change was made.

Data FieldsData Fields

ChangeTypeChangeType An indication of the nature of the change.

StatusStatus The status of this Component after the change.

ReasonReason An optional text Description of the reason for the change.

Historical RelationshipsHistorical RelationshipsKey Fields

RelationshipId The unique SNOMED CT Identifier of this Relationship.

Data Fields

ConceptId1 The unique SNOMED CT Identifier of the Concept which is the source of this Relationship.

RelationshipType The unique SNOMED CT Identifier of the Concept which represents the type of relationship between the related Concepts.

ConceptId2 The unique SNOMED CT Identifier of the Concept which is the target of this Relationship.

CharacteristicType An indication of whether a Relationship specifies a defining characteristic of the source Concept or a possible qualifying characteristic of that Concept.

Refinability An indication of whether it is possible to refine the target Concept when this relationship is used as a template for clinical data entry.

RelationshipGroup An integer value that links together Relationships which are part of a logically associated Relationship group.

Historical RelationshipsHistorical Relationships

• Allowed attribute values• SAME AS (redundant)• MAYBE A (ambiguous - 2 or more)• REPLACED BY (major changes)• WAS A (IS A no longer valid)• MOVED TO (namespace change)• MOVED FROM (namespace change)

Relationships TableRelationships TableKey Fields

RelationshipId The unique SNOMED CT Identifier of this Relationship.

Data Fields

ConceptId1 The unique SNOMED CT Identifier of the Concept which is the source of this Relationship.

RelationshipType The unique SNOMED CT Identifier of the Concept which represents the type of relationship between the related Concepts.

ConceptId2 The unique SNOMED CT Identifier of the Concept which is the target of this Relationship.

CharacteristicType An indication of whether a Relationship specifies a defining characteristic of the source Concept or a possible qualifying characteristic of that Concept.

Refinability An indication of whether it is possible to refine the target Concept when this relationship is used as a template for clinical data entry.

RelationshipGroup An integer value that links together Relationships which are part of a logically associated Relationship group.

Concept -> RelationshipConcept -> Relationship

72704001727040011166760081166760087162000071620000

Concept IDConcept IDRelationship IDRelationship IDConcept IDConcept ID

Relationship Table

Fracture (morphology)Fracture (morphology)M-12000M-120007270400172704001

Associated MorphologyAssociated MorphologyG-C504G-C504116676008116676008

Fracture of FemurFracture of FemurDD-13100DD-131007162000071620000

Concept NameConcept NameSNOMED IDSNOMED IDSCT IDSCT ID

Concepts Table

SCTIDSCTID• The SCTID data type is a 64-bit integer, which

is subject to the following constraints:• Only positive integer values are permitted.• The minimum permitted value is 100,000 (6 digits)• The maximum permitted value is

999,999,999,999,999,999 (18-digits).• As result of rules for the partition-identifier and

check-digit, many integers within this range are not valid SCTIDs.

SCTIDSCTID• The SCTID does not contain semantic information

related to the meaning of a concept or term• It does however have a structure that is designed to

allow different types of terminological components to be recognized. • The nature of a component can be derived from the table in

which a component is distributed. • Partitioning the SCTID avoids reuse of the same identifier for

a different type of component – thus avoiding ambiguity.• This also allows the nature of the identifier to be recognized

when stored in a record or transferred in a message.

SCTIDSCTID

SCTID for centrally distributed component.

SCTIDSCTID

SCTID for a component in an extension.

SCTID Partition ValuesSCTID Partition Values00 A concept

01 A description

02 A relationship

03 A subset

04 A Cross Map set

05 A Cross Map target

10 A concept in an extension

11 A description in an extension

12 A relationship in an extension

13 A subset in an extension

14 A Cross Map set in an extension

15 A Cross Map target in an extension