SPARQL editors playing with non-quoting reification syntax

SPARQL editors drafts have gone back and forth between
using turtle/N3 syntax for patterns and using RDQL (s p o)
syntax. The WG adopted "turtle + variables" on 8 March.

Since then, in response to comments on the spec, the editors
have added shorthand syntax for reification:


[[[
 << ?s ?p ?o >> :saidBy "Bob" .

is short for the triple patterns:

  _:b34  rdf:subject    ?s .
  _:b34  rdf:predicate  ?p .
  _:b34  rdf:object     ?o .
  _:b34  :saidBy        "Bob" .
]]]
 -- http://www.w3.org/2001/sw/DataAccess/rq23/#syntaxMisc
  Revision: 1.290 2005/04/01 15:29:04
  (and back to Revision 1.242  2005/03/14 )


This is the sort of reification that does *not* quote
the terms. i.e. we have

  << Mary hit [ a Ball ] >> rdf:subject [ a Person ].

not

  << Mary hit [ a Ball ] >> rdf:subject [ a Term ].


So it *does* follow from...

  Lois believes << Superman a Hero >>.
  Superman = ClarkKent.

that

  Lois believes << ClarkKent a Hero >>.

The N3 {}s do quote terms, so it does *not* follow
from

  Lois believes { Superman a Hero }.
  Superman = ClarkKent.

that

  Lois believes { ClarkKent a Hero }.


There's also the business of quoting multiple triples. The design
doesn't allow
  SELECT ?who
   WHERE ?who :said << ?anmial1 :eats ?animal2.
                       ?animal2 :eats ?animal3 >>.


Hmm... how do []s inside <<>> work? I think

  << Mary hit [ a Ball ] >> a FunnyThingToSay

actually reduces to

  << Mary hit _:something >> a FunnyThingToSay
  _:something a Ball.



I really wish RDF Core had deprecated rdfs:subject/predicate/object
because they don't get this quoting stuff right.
But they/we didn't. And DAWG has gotten comments from various
people that are using it and want syntactic support in SPARQL.

Maybe they/we should get some comments arguing against
this sort of reification syntax.


-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E