XLIFF 2.0 Comments - Matches origin and subType

I’m wondering about the intended use of origin in the <mtc:matches> module. Back to an example I’ve used with TC members in the past: Say I have a in context match (icm) coming from a translation memory (tm)
 I could define it like this:

 

<mtc:matches type=”icm” subtype=”tm”>

 

Would it be equally valid to do this?

 

<mtc:matches type=”icm” origin=”tm”>

 

The definition of origin and subType are both very loose, which makes me wonder if for the sake of interoperability there needs to be a stronger definition for origin perhaps.

 

Also, subType is missing from the attributes list in section B.1.2.3, even though there is an entry for it in B.1.3.7.

 

Thanks,

Ryan