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This has gotten kind of confused.

When I talk about merging data, I'm talking about taking two independent documents:

   <brian> parentOf <bct>
   <brian> name 'Brian'

   <bct> name 'Brendan'
and being able to join those graphs on the <bct> node, to say that a person named Brendan has a parent named Brian. This is what TimBL means by combining data from multiple applications (IMO).

This is trivial for software to do and takes a lot of the effort out of merging datasets. It's what makes the semantic web a web; you're linking different datasets together. I don't see how Shirky's arguments apply here.


When I say "inferencing", I mean something like Swish http://www.ninebynine.org/RDFNotes/Swish/Intro.html#ScriptEx... does.

Given two statements:

    <brian> parentOf <bct>
    <bct> gender <male>
and an appropriate set of rules, an inference engine can create a third statement:

    <bct> sonOf <brian>
This is what I understand Shirky's article to be about. IMO the applications of it are limited. It can also lead to the ridiculous results Shirky suggests.

Enabling inferences of this kind is neat, and it may be useful in the future, but it's not what the semantic web is About.

Your first example takes

    <brian> parentOf <bct>
    <brian> name 'Brian'
    <bct> name 'Brendan'
and deduces

    'Brendan' hasParentNamed 'Brian'
How is this substantially different from the second example? Forgive me if I'm thick; I'm honestly trying to understand.

It's not deducing a third property "hasParentNamed".

It's joining the two graphs so that you can do a query like this:

    SELECT ?parentName WHERE
      ?child name 'Brendan'
      ?parent parentOf ?child
      ?parent name ?parentName
to find the name of Brendan's parent.

You're being quite patient with me, thanks. :)

Still not getting it, here's your second example in that syntax:

      <brian> parentOf ?son
      ?son gender <male>
What's the fundamental difference? That one example yields a new RDF triple, and the other yields a query result? Surely this is just a matter of representation.

Good point. I think you've changed my mind about the utility of inferencing :).

The difference between querying and inferencing isn't what I was trying to emphasise, though. My point was the difference between being designed for making queries/inferences within a dataset, and being designed for joining distinct datasets.

Querying within a dataset is easy: SQL, XPath, XQuery, LINQ, etc. You can write rules for transforming any data model that you can query.

RDF isn't anything special in these areas (though I do think that SPARQL is an awfully nice query language). What it gives you is a way to link and merge datasets.

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