Re: Response to QA comments, Comment on QA draft

Jim Hendler wrote:

> 
> [snip]
> 
> Sandro:
> 
>>   Guideline 9. Allow extensions or NOT! [6]


Perhaps I don't understand ...

I have been thinking for a bit that OWL DL is not perfect but ...

e.g. QCRs well, one could have a nonstandard extension to OWL DL that 
supported them.

e.g. cycles of bnodes forming unnamed individuals; one could permit them in 
a nonstandard extension

e.g. predicates involving more than one data value; one could permit them 
in a nonstandard extension

e.g. URIs for user defined XML Schema simple types; Jena already does allow 
them in the de facto non standard extension

Obviously one needs a strict mode which switches any of this off, but I am 
not sure what simply forbidding extensions buys us.

It seems more to the point to say that extending OWL DL, takes you into OWL 
Full, in which the degree of interoperability expected is lower. Such 
extensions seem to be natural.

Jeremy