BLD: two issues with the BNF

I uncovered two issues with the BNF in BLD.  For me they are not 
critical for last call, but for some they might be.

The first issue is an error: Profile is not a Unicode string in the 
presentation syntax, but it is a term (see section 2.4).
The second issue is not an error, but it can be considered misleading 
(the BNF is too liberal): in the presentation syntax, rules are 
quantified rule implications.  So, an atomic formula is not a rule and 
may thus not be directly included in a group.  According to the BNF, an 
atomic formula can be considered a rule; this is misleading.

Best, Jos
-- 
                          debruijn@inf.unibz.it

Jos de Bruijn,        http://www.debruijn.net/
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