ISSUE-85: Optional restrictions

Issue 85 is mainly related to the behaviour of query engines, and so  
seems to me to be beyond the scope of this WG. Moreover, the extended  
annotation mechanism of OWL 2 could be used to get some or all of the  
desired behaviour if used with a suitable query engine. Beyond this,  
I don't think it is realistic to imagine that we will extend OWL 2 in  
the direction suggested (i.e., with optional restrictions) -- I'm not  
sure what the semantics would be and I don't see evidence of support  
from implementers.

I would therefore like to propose closing this issue as postponed,  
but I wanted to at least offer the chance for people to comment  
before putting such a proposal before the WG.

Ian