externalRef versus include

I'm having a hard time fully understanding the 
difference between <externalRef> and <include>. I realize 
<include> can only appear as a child of a <grammar> element whereas 
<externalRef> is not limited in this way. On the other hand, I'm not sure 
when you would want to use <include> but not <externalRef>. Am I 
right in assuming that the only circumstance where you would *have* to use 
<include> instead of <externalRef> is when you want to combine 
definitions from multiple grammars (using the "combine" attribute)?

 

Maybe the tutorial needs to say something about 
<externalRef> versus <include>, or at least this topic should be 
covered in the FAQ.

 

Josh

Joshua Lubell, NIST
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Gaithersburg MD 20899-8263 USA
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