# Generating Identifiers

## Generating SNOMED CT Identifiers

The following guidance is provided for organizations which have been issued namespace identifiers to create content in their own extension:

* Organizations must only generate new SCTIDs for components using a namespace identifier assigned to them by SNOMED International
* Organizations must have a mechanism in place to ensure that each SCTID is assigned only once. Generally, a single authority that generates *item-identifiers* in a sequential fashion for each type of component will achieve this goal.
* *item-identifiers* should not be generated so as to have meaning. They should be regarded as meaningless numbers. (Recall that an item identifier precedes the namespace identifier in an SCTID.)

## Generating UUIDs

Reference Set Members are identified with UUIDs instead of SCTIDs, so extension producers will also need the mechanism to generate UUIDs. UUID stands for Universally Unique Identifier, and each UUID is represented as a 128-bit number.

UUIDs are globally used to identify information in computer systems and they are for practical purposes unique, without depending on a central registration authority or coordination between the parties generating them. While the probability that a UUID will be duplicated is not zero, it is close enough to zero to be negligible.

Thus, anyone can create a UUID and use it to identify something with near certainty that the identifier does not duplicate one that has already been, or will be, created to identify something else. Information labeled with UUIDs by independent parties can, therefore, be later combined into a single database, or transmitted on the same channel, without needing to resolve conflicts between identifiers.

Several online platforms are available providing support for generating UUIDs, and for parsing their textual representation.

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