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.