An attribute represents a characteristic of the meaning of a concept or the nature of a refinement.
Example: 116676008 | Associated morphology
- Concept Model Attribute
- Relationship Type
Attribute value pair
A combination of an attribute name and an attribute value used to represent a specific type of information in a generic way without altering the underlying structure of an information model. The attributename identifies the type of information and the attribute value provides a value.
A computer application or software tool used for exploring and searching terminology content. A typical SNOMED CT browser can locate concepts and descriptions by Identifiers and by searching the text of description terms. Various views of located concepts may be displayed including the set of related descriptions, the hierarchical relationships and other defining relationships.
SNOMED CT browser
The check-digit is the final (rightmost) digit of the SNOMED CT Identifier (SCTID). It can be used to check the validity of SCTIDs. Clinical Information Systems can use the check-digit to identify SNOMED CT codes that have been entered incorrectly (typo errors, etc). It is calculated using the Verhoeff algorithm.
SNOMED CT Component
Refers to any item identified by an SCTID in the main body of SNOMED CT, or in an authorized Extension. The partition-identifier indicates the type of component referred to by that SCTID. Each component is a uniquely identifiable instance of one of the following:
A clinical idea to which a unique Concept Identifier has been assigned. The term concept may also be used informally with the following meanings:
- The concept Identifier, which is the key of the Concept file (in this case it is less ambiguous to use the term "conceptId" or "concept code");
- The real-world referent(s) of the Concept Identifier, that is, the class of entities in reality that the Concept Identifier represents (in this case it is less ambiguous to use the term "meaning" or "code meaning").
- SNOMED CT concept
Equivalence is the state of two SNOMED CT concept codes or postcoordinated expressions having the same meaning. Concept equivalence can occur when a postcoordinated expression has the same meaning as a precoordinated concept code; or when two different postcoordinated expressions have the same meaning.
ConceptId (field in RF1)
A SNOMED CT Identifier that uniquely identifies a Concept (meaning).
Example: For the meaning named | Pneumonia (disorder) |, the ConceptId is 233604007.
Concepts table (RF1)
A table that includes all SNOMED CT concept codes. Each concept code is represented by a single row.
A distribution file used to represent the main SNOMED CT components (concepts, descriptions and
SNOMED CT core
SNOMED CT core table
SNOMED CT core file
Cross Map (RF1)
A Cross Map is a reference from a Concept code to a Cross Map Target. Each Cross Map is represented as a row in the Cross Maps Table. It links a single SNOMED CT concept code to one or more codes in a target classification (such as ICD-9-CM) or terminology. A Concept code may have a single Cross Map or a set of alternative Cross Maps
CTV3ID (field in RF1)
A five-character code allocated to a meaning or term in Clinical Terms Version 3 (CTV3, previously known as Read Codes). Each row in the SNOMED CT concepts table has a field for the corresponding concept code from CTV3.
Note: The CTV3ID and SNOMEDID fields are no longer supported in Release Format 2. Instead a |Simple map (reference set)| is used to document the link between legacy codes and SNOMED CT.
Note: The CTV3ID field should no longer be relied upon for mapping to and from the Read Codes. Additional mapping work in the UK identified some anomalies and resulted development of more flexibility table for Read Code Mapping
An association between a human-readable phrase (term) and a particular SNOMEDCTconcept code. Each
description is represented by a separate row in the Descriptionfile.
- SNOMED CT description
DescriptionId (field in RF1)
A SNOMED CT Identifier that uniquely identifies a Description.
Descriptions table (RF1)
A data table consisting of rows, each of which represents a Description.
A language modified by the vocabulary and grammatical conventions applied to the language of a particular geographical or cultural environment.
A software application designed to support the use of SNOMED CT.
SNOMED CT enabled application
SNOMED enabled application
SNOMED CT application
SNOMED CT Extension
A set of terminology components and derivatives that add to and are dependent on the SNOMED CT International Edition, and are created, structured, maintained and distributed in accordance with SNOMED CT specifications and guidelines.
- Components that are created in an extension are identified using extension SCTIDs. These identifiers include an extension namespace which ensures that they do not collide with other SCTIDs, and can be traced to an authorized originator.
- Namespace identifiers are allocated in response to requests from IHTSDO Members and Affiliates. For further information about this process and for access to the current SNOMED CT Namespace Register please refer to the IHTSDO web page on Namespaces.
- IHTSDO Members may create, maintain and distribute extensions to address specific national, regional and language requirements. IHTSDO Affiliates may also create, maintain and distribute extensions to meet the needs of particular software solutions and customers.
- See also Edition which refers to the combination of an extension with the International Release and, where relevant, any modules from other extensionson which it depends.
Fully defined concept
- Sufficiently defined concept
FullySpecifiedName (field in RF1)
A term unique among active Descriptions in SNOMED CT that names the meaning of a Concept code in a manner that is intended to be unambiguous and stable across multiple contexts.
An ordered organization of concept codes linked together through | is a | relationships. Concept codes linked to their more general parent concept codes directly above them in a hierarchy Concept codes with more general meanings are usually presented as being at the top of the hierarchy and then at each level down the hierarchy code meanings become increasingly more specific or specialized . Formally, a hierarchy is represented as a Directed Acyclic Graph.
History mechanism (RF1)
The history mechanism is the information distributed with SNOMED CT designed to track the history of changes to its logic definitions and descriptions. The history mechanism is supported by two distribution tables:
- Component History Table
- References Table
SNOMED CT Identifier
A unique integer identifier applied to each SNOMED CT component (Concept, Description, Relationship, Subset, etc.). Each SCTID includes an item identifier, a check-digit, a partition identifier and, depending on the partition identifier, may also include a namespace identifier.
Concepts that cannot be fully defined using the current concept model are called primitive concepts. Primitive concepts cannot be fully acted upon by the classifier; consequently subtype concepts are not assigned via the classification process. Instead, to create subtypes, each relevant concept must be identified and the IS_A relationship stated manually.
SNOMED CT International Release
The set of release files provided on a specified release date, to represent the part of the content of SNOMED CT that forms the common foundation to the terminology available to all IHTSDO Members and Affiliates.
- The International release, provided by the IHTSDO, may be supplemented by Extension releases provided by IHTSDO Members and Affiliates to meet additional national, local and organizational requirements.
- See also International Edition which refers to the same general content, without specifying a particular release date.
For purposes of SNOMED CT translations, a language is a vocabulary and grammatical form that has been allocated an ISO639-1 language code. See also dialect.
Language subset (RF1)
SNOMED CT can be translated into virtually any human language or dialect. These translations attach new language -specific terms as descriptions of existing concept codes and may also use existing descriptions if translation is not necessary. A language subset is a set of references to the descriptions that are members of a language edition of SNOMED CT. Additionally, data in the language subset specifies the DescriptionType of each description (Fully Specified Name, Preferred Term or Synonym).
A set of data structures for representing maps to other terminologies and classifications. The Mapping Mechanism data structures are distributed as three tables:
- Cross Map Sets Table
- Cross Maps Table
- Cross Map Targets Table
A person who directly edits the logic definitions and other structures of the terminology; aka Clinical Editor or Terminology Manager.
SNOMED CT modeler
SNOMED CT author
The process of editing logic definitions to reflect the meaning intended by the Fully SpecifiedName.
SNOMED CT modeling
SNOMED CT authoring
A seven digit number allocated by the IHTSDO to an organization that is permitted to maintain a SNOMED CT Extension. The namespace identifier forms part of the SCTID allocated every component that originated as part of an Extension. Therefore, it prevents collision between SCTIDs issued by different organizations . The namespace-identifier indicates the provenance of each SNOMED CTcomponent.
about the origin of the component
Extension namespace identifiers
The second and third digits from the right of the string rendering of the SCTID. The value of the partition-identifier indicates the type of component that the SCTID identifies (e.g. Concept, Description, Relationship, etc) and also indicates whether the SCTID contains a namespace identifier.
Representation of a clinical meaning using a combination of two or more concept identifiers is referred to as
Example: SNOMED CT includes the following concepts:
125605004 | fracture of bone |
363698007 | finding site |
71341001 | bone structure of femur |
SNOMED CT also includes a precoordinated concept for 71620000 | fracture of femur |. Therefore It is possible to represent the clinical meaning "fracture of femur" in different ways:
as a precoordinatedexpression:
71620000 | fracture of femur |
or as a postcoordinatedexpression:
125605004 | fracture of bone | : 363698007 | finding site | = 71341001 | bone structure of femur |
Representation of a clinical meaning using a single concept identifier is referred to as a precoordinated expression.
Note: In contrast, expressions that contain two or more concepts Identifier are referred to as postcoordinated expressions. For more information and examples see the glossary entry for postcoordinated expression.
A concept with a formal logic definition that is not sufficient to distinguish its meaning from other similar concepts
Example: The concept 5596004|atypical appendicitis (disorder)| is primitive because the following definition is not sufficient to distinguish "atypical appendicitis" from any other type of "appendicitis".
- •116680003 | is a | = 74400008 | appendicitis |
- 116676008 | associated morphology | = 23583003 | inflammation |
- 363698007 | finding site | = 66754008 | appendix structure |
Figure 15: Definition of: |atypical appendicitis (disorder)| (primitive)
An attribute-value relationship associated with a concept code to indicate to users that it may be applied to refine the meaning of the code. The set of qualifying relationships provide syntactically correct values that can be presented to a user for postcoordination. Example: 'Revision status ' = 'First revision' is a possible qualifying characteristic of 'Hip replacement'. A qualifying characteristic is contrasted with a defining characteristic. It is referred to in CTV3 as a 'Qualifier.
A sphere of authority, expertise, or preference that influences the range of components required, or the frequency with which they are used. A Realm may be a nation, an organization , a professional discipline, a specialty, or an individual user.
An association between a source concept and a destination concept. The nature of the association is indicated by a reference to another concept referred to as the relationship type.
- Each relationship provides information about the source concept. In the example below
- Relationships are represented by rows in the Relationship File
Table 90: Illustrative example of aRelationship
finding site |
SNOMED CT relationship
RelationshipType (field in RF2)
The nature of a Relationship between two Concepts. Relationship Types are represented in SNOMED CT by Concept codes. In the Relationships Table, the RelationshipType field contains the ConceptId for the concept in SNOMED CT that forms the relationship between two other concepts (ConceptId1 and ConceptId2). For defining and qualifying relationships, the Relationship Type is an Attribute code. RelationshipType should not be confused with CharacteristicType.
RelationshipId (field in RF2)
A SNOMED CT Identifier that uniquely identifies a Relationship. RelationshipId is the key of the Relationships Table. Each row in the Relationships Table represents a relationship triplet (ConceptId1 RelationshipType - ConceptId2).
Relationships table (RF1)
A data table consisting of rows, each of which represents a Relationship.
SNOMED CT Release
The content of a version of a SNOMED CT Edition that has been made available to licensees at a particular point in time.
The single concept that is at the top of the | SNOMED CT Concept | hierarchy.
Root metadata concept
The single concept that is at the top of the | SNOMED CT Model Component (metadata) | hierarchy.
concept may not be present in some Release Format 1 files.
Root metadata code
An acronym for the SystematizedNomenclature of Medicine originally developed by the College of American Pathologists and now owned and maintained by the IHTSDO. SNOMED Clinical Terms is the most recent version of this terminology. It was preceded by SNOMED RT and SNOMED International.
SNOMED Clinical Terms
SNOMED CT is a clinical terminology maintained and distributed by the IHTSDO. It is considered to be the most comprehensive, multilingual healthcare terminology in the world. It was created as a result of the merger of SNOMED RT and NHS Clinical Terms Version 3.
- SNOMED CT
Sufficiently defined concept
A concept with a formal logic definition that is sufficient to distinguish its meaning from other similar concepts.
See also primitive concept.
Example: The concept 74400008|appendicitis (disorder)| is sufficiently defined by the following definition because any concept for which this definition was true would be the disorder "appendicitis".
- 116680003 | is a | = 18526009 | disorder of appendix |
- 116680003 | is a | = 302168000 | inflammation of large intestine |
- 116676008 | associated morphology | = 23583003 | inflammation |
- 363698007 | finding site | = 66754008 | appendix structure |
Figure 16: Definition of: |appendicitis (disorder)| (sufficiently defined)
- Fully defined concept
A set of components which part of and fully included with a larger set (e.g. a specified set of Concepts or Descriptions)
- In Release Format 2 the standard way to represent a subset of components is by using a Simple Reference Set
- In Release Format 1 the term subset has the following special meaning:
- A group of components (e.g. Concepts, Descriptions or Relationships) that share a specified common characteristic or common type of characteristic. Subsets represent information that affects the way the components are displayed or otherwise accessible within a particular realm, specialty, application or context.
This special meaning arose from the "Subset Mechanism" which has now been replaced by Reference Sets. Therefore, except when referring to RF1 files the term subset should should now be used for its more correct general meeting.
A term that is an acceptable way to express a the meaning of a SNOMED CT concept in a particular language.
Synonyms are represented as SNOMED CT descriptions with the typeId value 900000000000013009
- Synonyms allow representations of the various ways a concept may be described.
- Synonyms (unlike fully specified names) are not necessarily unique because the same term can be used to describe more than one concept.
- The preferred term is the synonym marked as preferred for use in the Language reference setfor a given language or dialect.
Top level concept code
A Concept Code that is directly related to the Root Concept Code by a single Relationship of the Relationship Type | is a |. All Concept Codes (except for metadata concepts) are descended from at least one Top-Level Concept Code via at least one series of Relationships of the Relationship Type"| Is a | ".
Top level metadata code
A Concept Code that is directly related to the RootMetadataCode by a single Relationship of the RelationshipType | is a |. All Metadata Concept Codes are descended from at least one Top-Level Metadata Concept Code via at least one series of Relationships of the Relationship Type " Is a | ".