CCD ClinicalDocument.id: What is the value of root supposed to be?

Question

In the CDA R2 CCD implementation guide, a ClinicalDocument element (the root element of the document) is supposed to have an id element.

This id element is of the "II" datatype: http://wiki.hl7.no/index.php/R1:II This states that the root attribute is to have an OID value, to identify the type of identification used in the extension attribute.

Now, when looking at the sample CCD document that HL7 provides we see:

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="CDASchemas\cda\Schemas\CCD.xsl"?>
<ClinicalDocument xmlns="urn:hl7-org:v3" xmlns:voc="urn:hl7-org:v3/voc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:hl7-org:v3 CDA.xsd" >
...
   <id root="db734647-fc99-424c-a864-7e3cda82e703"/>
...
</ClinicalDocument>

The root value db734647-fc99-424c-a864-7e3cda82e703 is not an OID. I'm not sure what it is, but it looks like a UUID perhaps? Anyway, is this a static value for all CCD documents, or will it differ from document to another? Why is the extension attribute not used, isn't that what identifies the document?

Note that throughout that same sample document I also see things like

<id root="2.16.840.1.113883.19.5" />

which seem to be OIDs (in the root attribute).

EDIT: The sample document I reference is from the HL7 CCD implementation guide, i.e it is from the official source, it is unlikely that they would have a glaring error in their sample file that nobody has noticed before.

Answer 1

Old question, I know, but I'm just learning about this stuff and I think I finally have my head wrapped around it.

The roots are basically like namespaces or domains in which the id will be valid and guaranteed to be unique. For example if your authority/organization is generating CDAs it will most likely have applied for a unique OID (the value you see in the root is an OID 2.16.840.1.113883.19.4).

So, for the example above,

    <id root="2.16.840.1.113883.19.4" extension="abc266"/>

I'm going to guess that 2.16.840.1.113883.19 is the base OID for the authority sending out the CDA and the .4 is most likely the OID to indicate that this

<id>

is in fact the document's identifier (the authority defines these OID extensions under the base OID)

"extension" is the Unique Identifier value for this particular document.

In regards to your comment about the implementation guide not having glaring errors, I've found quite the opposite in trying to figure this stuff out...there are errors abound. I do believe the root is always to be an OID, the extensions are usually UUIDs or some other unique ID.