does negation draw from partition?

[ericprud]

What do people mean by ! in a triple pattern?

I propose that it is that there are no corresponding triples in the neighborhood (as opposed to the partition). For instance:

<S> {
  (foaf:name . | foaf:givenName .; foaf:familyName ); # either a name or components
  foaf:shoeSize .;
  (foaf:homepage .; ! foaf:name .)? # no foaf:homepage if there's a foaf:name.
}

would pass <s> foaf:name "Bob"; foaf:homepage <http://...> . if negation draws from the partition but fail if it draws from the neighborhood. IMO, the author's intent is that it fail. There are other ways of expressing this, e.g.

<S> {
  (  foaf:name .; foaf:homepage .?
   | foaf:givenName .; foaf:familyName );
  foaf:shoeSize .
}

but they require reordering the properties which is a problem for e.g. FHIR where we use the order to convert RDF to an ordered XML document.

I believe this is easy to document and implement, but let me know if you disagree. See matches TripleConstraint