8.2 ISO_OID
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## 8.2 ISO_OID

ISO 8824 and ISO 9834-1 are the standards defined for the generation of object identifiers that are used as DICOM Unique Identifiers (see PS3.5), can also serve as a general mechanism for identifying organizations and objects defined by those organizations.

When the Coding Scheme Designator is ISO_OID, the Code Value shall be the numeric (dot delimited) form of a valid object identifier.

A repository of known existing object identifiers can be found at http://www.oid-info.com/index.htm. For example:

- the ISO 9834-1 assigned numeric object identifier for the country France, is "1.0.3166.2.2.1.250" (since ISO 3166 defines a means for maintaining country codes using object identifiers)

- the object identifier for the RIPEMD-160 cryptographic hash function is "1.0.10118.3.0.49"

- the object identifier for the HL7 V2 table of codes for marital status is "2.16.840.1.113883.12.2"

The re-use of object identifiers for existing concepts that do not have an alternative more appropriate coding scheme compatible with DICOM provides a mechanism to avoid defining new codes. For example, HL7 assigned object identifiers can be found at http://www.hl7.org/oid/index.cfm.

Though the intent of ISO_OID is to define organizational roots for the hierarchical assignment of object identifiers, and not specifically to identify organizations per se, the organizational root values can be construed as identifying the organization. For example, the DICOM Standards Organization itself can be identified by the value "1.2.840.10008". See also CID 5002 “Organizations”.

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