Re: [PRD] class membership assertions

Ah yes, I missed the restriction on well-formed action blocks.
So, there is no discrepancy. Glad to find out I was wrong :)

Cheers, Jos

On Wed, May 12, 2010 at 1:17 PM, Christian De Sainte Marie
<csma@fr.ibm.com>wrote:

>
> Hi Jos,
>
> Jos wrote on 12/05/2010 11:01:05:
>
> >
> > I found a strange discrepancy in PRD. In the definition of assert
> > fact actions [1], it is possible to assert class membership facts.
> > Now, I understand that there is a shortcut syntax for asserts in the
> > XML [2] and presentation [3] syntaxes. In particular, it's not
> > necessary to write the "Assert" for positional and frame atoms.
> > However, if one wants to assert a class membership formula, one is
> > required to write the "Assert".
> > Why is there this discrepancy? Was that an oversight?
>
> The reason is that the "Assert-free" syntax is the recommended syntax for
> PRD rules that are also Core.
>
> But the assertion of a class membership is allowed, in PRD, only for newly
> created instances, that is, inside a Do, and after an action variable has
> been bound using the New construct [1]: in other words, a PRD rule that
> asserts a class membership cannot be Core, and the "Assert-free" syntax
> would not make sense in that case (even for positional atoms and frames, the
> "Assert-free" syntax is not allowed inside a Do).
>
> [1]http://www.w3.org/TR/rif-prd/#def-wf-action-block
>
> Cheers,
>
> Christian
>
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Jos de Bruijn
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