W3C home > Mailing lists > Public > semantic-web@w3.org > March 2011

Re: thisiness

From: Nathan <nathan@webr3.org>
Date: Fri, 25 Mar 2011 12:36:59 +0000
Message-ID: <4D8C8C6B.7030203@webr3.org>
To: Henry Story <henry.story@bblfish.net>
CC: Gregg Reynolds <dev@mobileink.com>, SW-forum Web <semantic-web@w3.org>, Pat Hayes <phayes@ihmc.us>
Henry Story wrote:
> On 25 Mar 2011, at 12:38, Gregg Reynolds wrote:
>> (BTW, there are no unlabeled nodes; what seem to be unlabeled nodes are in fact anaphorically or indexically labeled.  An unlabeled circle in a diagram is still a symbol, a kind of indexical label; where nesting is used syntactically to indicate a blank node, the syntactic device of nesting can be taken as a kind of indexical label or symbol.  In other words, the difference is not between labeled and unlabeled, but between persistently and transiently labeled (or: between rigidly and contigently labeled) nodes.)
> yes, that is what I was getting at in my last post. Blank nodes allow non rigid designation. URIs tend to be rigid designators. Somehow in philosophy this distinction seems to have been very helpful. It would be interesting to follow through on this parallel and see if we don't find the same usage and value on the semweb.

We have the term "blank node identifiers" which leads many to believe 
that the identifier names the blank node, but there is no scope for that 
name, so they are non-rigid designators. The problem is that now often 
many see certain sets of triples as being associated with a name somehow 
  (as in sparql, the ?g, and linked data, the <uri> you GET) which gives 
a scope for the name, and thus the expectation is that blank node 
identifiers are rigid designators within the scope of that name. (As in, 
a name which acts as a namespace and defines a universe within which 
blank nodes can be both quantified and identified/named).

Blank nodes are pretty much existentially bound variables with a 
quantifier whose scope is the entire graph, so when you have a name for 
two graphs and the name is the same, it follows that they are thought of 
as bound variables rather than free variables.

Even if the above were made so in some way, we'd arguably end up with 
even more unexpected functionality when merging graphs associated with 
different names, and when no name is present.


Received on Friday, 25 March 2011 12:38:10 UTC

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