[osis-core] ID confusion

[Harry Plantinga]

> So, for other texts, Josephus for example, do we need to allow other 
> elements to have something like verseID that will allow them to have a 
> canonical reference without overloading ID or should we simply overload 
> ID and document it?

Let's see. Suppose I have two different instances of Matthew 3:2 in my 
document, one Greek and one English.

If these canonical identifiers like Matt.3.2 are also XML IDs, I wouldn't
be able to mark both of them as being Matt.3.2.  Would I want to be able
to re-use "Matt.3.2" like that?

I tend to think you wouldn't want to have two Matt.3.2's in your document;
that would make it hard to get to the one you want. 

-Harry