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HL7 use of UIDs & ISO current WI

HL7 use of UIDs & ISO current WI. Nicholas Brown DICOM WG 10 London 2003. Object identifier needs. Which it is (globally unique) Who created it Where the master copy is to be found Where a local copy is available for rapid access

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HL7 use of UIDs & ISO current WI

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  1. HL7 use of UIDs & ISO current WI Nicholas Brown DICOM WG 10 London 2003

  2. Object identifier needs • Which it is (globally unique) • Who created it • Where the master copy is to be found • Where a local copy is available for rapid access • ‘Which’ and ‘where’ may be combined into one field but this is not thought to be a good idea by some but may not be too bad according to Fred!

  3. HL7 Ver 3 Provision & text 1 • Defines UID data type • 2 main fields called • Root • Extension • Implied use: extension is locally unique user friendly identifier. If absent root is the UID. If present concatenate root and extension to obtain globally unique ID

  4. HL7 Ver 3 Provision & text 2 Text description makes clear that the specification of root is as a globally unique identifier such as used by DICOM. In particular it says that semantics may be inferred but that this use is not supported by HL7 • Woody keen on use of GUIDs - 128 bit UIDs in Hex as used by Microsoft.

  5. HL7 Ver 3 Provision & text – problems ? • Maybe precludes the use of a globally unique UID such as DICOM uses and a locally unique user friendly ID ?? • Length not defined • (HL7 lengths are only recommended not mandatory) • Format not defined • Multiplicity? (maybe allows global and local) • How use Ver 3 to support need for 3 UIDs to identify and access a DICOM object?

  6. Current ISO WI for exchange format for UIDs • Explain use of UIDs • Feasibility and efficiency of fixed length • Justification for separating ‘which is it’ from who created object and where it can be found • Propose • 64 char alphanumeric string (supports 64 char DICOM and 32 char GUID) • Separator to be period • No leading or trailing spaces etc (current ISO logical only)

  7. HL7 view • Strong opposition to fixed length • Need to support customer request to combine ‘which is it’ and ‘where/who’ much more than 64 chars. • Combining classical ‘root’ and free format for local ID is a neat idea.

  8. IHE use of HL7 and DICOM • Conflict in use of UID may pose serious problems for interoperability of DICOM and HL7 Version 3 • Ver 3 ideas not yet tested in the real world

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