Use of UUIDs in II.extension
1. It's perfectly ok. The II.root represents the assigning authority which provides semantic context for the UUID issued.
So: which is it? (see the discussion page for details)
20070108 MnM/INM: Motion to add "The normal mechanism for transmitting a UUID (DCE Universal Unique Identifier) as an identifier is to send it as the root with no extension. A UUID expressed as an extension is not considered to be a match for a UUID in the root. I.e. A match is required on both root and extension to be considered a match. The root can be used to identify a namespace. The design of HL7 specifications SHALL never assume that receiving applications can infer the identity of the scoper or issuer, or the type of the identifier from the namespace identifier." to datatypes R2. (Grahame/ Lee, x-0-1)