told bnodes example

Re discussion of bNodes in different graphs discussion in today's
meeting, would an example of a bNode that has a sort of fixed place in
the universe help? I have been working on querying conventional
relational data with SPARQL. A simple interpretation of a row in the
Person table is a foaf:Person with some given name and other
attributes. We view the primary key as an encoding artifact of the
relational store and elect not to share that number with the outside
world.

   -- Person --
  primary key   given   email (unique key)
    21857       Eric    eric@w3.org
    31572       Eric    em@w3.org
  =>
  mbox a owl:inverseFunctionalProperty .
  [ a foaf:Person ;
    given "Eric" ;
    mbox <mailto:eric@w3.org> ] .
  [ a foaf:Person ;
    given "Eric" ;
    mbox <mailto:em@w3.org> ] .

I think this is a told blank node if my SPARQL impl *chooses* to
constrain
  SELECT mbox ?o WHERE { _:pk21857 mbox ?o }
to have a subject of the obvious primary key, yielding
  ?o
  <mailto:eric@w3.org>
Unconstrained, this would yield
  ?o
  <mailto:eric@w3.org>
  <mailto:em@w3.org>

This may help with Pat and Enrico's discussion, it may not...
-- 
-eric

office: +81.466.49.1170 W3C, Keio Research Institute at SFC,
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