Component Identifiers

Each SNOMED CT component is identified by a SNOMED CT identifier (SCTID) which is defined as follows:

A unique integer identifier applied to each SNOMED CT component (Concept, Description, or Relationship).

Each SNOMED CT Identifier (SCTID) includes an item identifier, a check-digit, a partition identifier and, depending on the partition identifier, it may also include a namespace identifier.

Reference Set Member Identifiers

Each reference set member is identified by a Universally Unique Identifier (UUID) which is defined as follows:

Universally unique identifier are generated by widely available algorithms. They are used to identify information in computer systems world-wide.
In SNOMED CT universally unique identifiers is used to uniquely identify reference set members. Since universally unique identifiers are unique and it is unnecessary to track the issuing of identifiers for the thousands of reference set members that are needed in some implementations.
In SNOMED CT release files, universally unique identifiers are represented as a string following a standard canonical form - a 36 character string containing 32 hexadecimal digits and four hyphens. The hexadecimal digits are arranged in five groups separated by the hyphens. The first group contains 8 hexadecimal digits, the last group contains 12 and each of the three other groups contains 4. So the overall pattern is 8-4-4-4-12.