5.2. SCTID Representation

Each SCTID (data type) identifies a SNOMED CT component.The identifier itself does not contain information related to the meaning of a conceptor description.This means it is not possible to infer anything about the meaning of a conceptfrom the numeric value of the identifier or from the sequence of digits in that form of the identifer. The meaning of a conceptcan be determined from relationshipsto other conceptsand from associated descriptionsthat include human readable terms.

The SCTID does however have a structure which includes valuable information about the nature and source of the identified component and the validity of the identifier. This structure supports the following features:

• Check-digitvalidation of the identifier.

  • The check-digitis the final digit in the decimal rendering of the identifier. This can be checked to minimize errors from transcription or incomplete copy-paste actions.

• Partitioning between identifiers for different types of SNOMED CT component.

  • A two-digit partition-identifierdistinguishes the identifiers of different component types and prevents the same identifier from being allocated to both a conceptand a description.As a result, when an SCTID is read from a record or other resource, it is possible to determine whether it represents a concept,a relationshipor a description,before searching for the identified component.

• Namespaces to separate component identifiers originated by different organizations. 

  • Organizations are only permitted to issue identifiers which fall within a specified namespace of potential identifier values. This prevents collisions between identifiers issues by different organizations which would otherwise result in ambiguity and errors when sharing data.

  • There are two formats used for representing namespaces. 

    • Short format in which partition-identifiersare reserved for an organization which is permitted to issue any valid identifiers within the allocated partitions. The short format approach does not require a specific namespace-identifierand is only applicable to components originated and maintained by the SNOMED Internationalas part of the International Releaseof SNOMED CT.

    • Long format in which the partition-identifiervalue indicates that a separate namespace-identifieris required to distinguish between components originated as part of an extensioncreated by an appropriately authorized organization .