Re: Difference for attribute values

[James Clark <jjc@jclark.com>]

> Is <not> for <text/> only, or is it for <data ..> as well?  If
> we allow <data> to have <not>, we have to use equality
> check.  But it's there already.

I think <not> and <difference> can work for both <text> and <data>.

<not>p1 p2 ... </not>

would be equivalent to

<difference> <text/> p1 p2 ... </difference>

I think we use the same restriction for <difference> as for attribute
values.  We just require that element and attribute are not allowed.  The
usual restriction on <data> will disallow groups of <data>.  We also need to
apply the same restrictions to

<difference> <text/> <data/> </difference>

that we apply to <data/>.

The inference rule would be simply

E; ns |- {}; v =~ p1 => k; kr   not(E; ns |- {}; v =~ p1 => k; kr)
----------------------------------------------------------------
E; ns |- {}; v =~ <difference> p1 p2 </difference> => k; kr

I don't think we need to do anything special to make <data/> work.

I have a lingering doubt about <not/>. People might expect

  <not><value>foo</value></not>

to match an element.

James