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Re: Structured Body: help

From: Robert Sanderson <azaroth42@gmail.com>
Date: Tue, 17 Jul 2012 18:02:04 +0200
Message-ID: <CABevsUGsNGToXSPHb4+gChuyFnUCnPopJNHuqoQARKfk0SjNxg@mail.gmail.com>
To: Christian Morbidoni <christian.morbidoni@gmail.com>
Cc: public-openannotation@w3.org
On Tue, Jul 17, 2012 at 5:45 PM, Christian Morbidoni
<christian.morbidoni@gmail.com> wrote:
> I'm vary happy that Named Graphs has been included in the specification as I
> think they are very useful.
> I'm in the process of modeling the Pundit (http://thepund.it) triplestore to
> conform to the relatively new specs.

Fantastic, that's great news Christian.  If there's anything that we
can help with, please feel free to ask!


> I have a couple of questions/doubts:
> "It is RECOMMENDED to have a dereferencable resource that contains the
> serialization of the graph, rather than to use Named Graphs."
> Does it means that Named Graphs, when used as body of an annotations should
> have URL and that this URL should be dereferenced to the triples contained
> in the named graph? If it is so I think it is a very good approach.

Yes, that's it exactly.  The issue with Named Graphs is that they have
their own serialization (eg Trig/Trix) which a regular RDF system may
not be expecting.
Thus, by removing the triples from the annotation graph, both
documents may be a regular RDF serialization.


> Regarding the Structured Body
> (http://www.openannotation.org/spec/extension/#StructuredBody): it seems a
> very strange approach to me.
> If there has already been a discussion about it please point me to it....I
> cannot find anything in the ML archive.

There hasn't been an online discussion about it, though it was
discussed at a face to face meeting in Boston in March.

> I'm referring to the example that uses X, Y, Z, etc. The question is: how do
> I distinguish triples that belongs to the structured body from other triples
> that state something about Y, Z or X?

Yes, if you store all of your annotations in a triplestore you can't
necessarily reconstruct what was originally part of the individual
annotations if you use this approach.  For example if someone were to
assert a relationship between Y and W, then this would get picked up
by the example annotation.  Hence the recommendation to keep the
triples as content of a separate document with a URI.


> May be the answer is in this sentence "Implementations that expect a
> resource with a serialization separate from the Annotation graph may not be
> able to store structured resources"?

Basically, as above, that systems built around the open world, single
graph model will not be able to reconstruct the individual annotations
unless they have some other means of storing the annotations (eg as
documents rather than triples)


> Does it mean that resource X, Y and Z
> should not be involved in triples other than the ones included in the
> structured body? Does it also mean that two different annotations cannot
> have structured bodies that talks about the same resource (e.g. Y)? Isn't it
> a bit too restrictive :-) ?

Indeed, very restrictive and impossible to enforce.  It's why we don't
recommend doing this unless without thinking long and hard about the
consequences or have a constrained system in which this isn't an issue
:)

Hope that helps,

Rob

PS. Are you around DH2012, I saw your name on the program?  I'll be
there tomorrow only if you'd like to meet in person to discuss. Email
me off-list if you'd like
Received on Tuesday, 17 July 2012 16:04:52 UTC

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