W3C home > Mailing lists > Public > public-data-shapes-wg@w3.org > December 2014

Re: ISSUE-5 Definition of Resource

From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
Date: Thu, 18 Dec 2014 20:31:52 -0800
Message-ID: <5493AA38.9040108@gmail.com>
To: Arthur Ryman <ryman@ca.ibm.com>, public-data-shapes-wg@w3.org
I would find it very useful to point to something that states that this is the 
way that things should work.


On 12/18/2014 12:55 PM, Arthur Ryman wrote:
> I'd like to summarize the discussion from the WG today and ask that we
> arrive at a consensus on the meaning of terms. Here are definitions that
> align with W3C specs.
>
>>From a web point of view, a resource is any identifiable thing. We
> identify them using URIs.

URIs identify or denote resources, yes.


>>From an HTTP point of view, there are two kinds of resource, namely
> information resources and real-world objects. The term "real-world object"
> denotes any resource that is not an information resource. This implies
> that fictional characters are real-world objects.

What makes information resources not be real-world objects?

> An HTTP server should return a 3XX response code when a real-world object
> URI that it hosts is requested via HTTP GET.

I'm uncertain as to the scoping here.  3xx is a redirection response, and can 
be used when a page has moved.  Does this mean that the page is not an 
information resource?

> The response should redirect
> to an information resource URI that has information about the real-world
> object.

Why?  Hash URIs can be used as non-information resource identifiers and I 
don't think that they work this way.

> An HTTP server should return a 2XX response code when an information
> resource URI that it hosts is requested via HTTP GET. The response should
> contain a representation of the information resource in some content type,
> ideally one of the content types given by the Accept header.
>
> For the purposes of the wg, we are interested in RDF content types.

Well for RDF graphs, certainly, but there may be other kinds of content that 
the WG might be interested in.

> An RDF representation consists of a set of triples which can be thought of
> as forming a graph, technically a directed, labelled graph.

A document with an RDF content type encodes an RDF graph, which can be thought 
of as a directed edge- and node-labelled multi-graph where the node labels are 
unique and there is at most one edge with a particular head, tail, and edge label.

> The nodes in an RDF graph are labelled by RDF terms, i.e. URI, Literal,
> and Blank Node. The arcs are labelled by URIs. There are other constraints
> defined in the RDF specs.

Indeed.

> Since we can visualize graphs as geometric objects,

Graphs only act like geometric objects in limited ways.

> the term "shape" has
> been adopted to describe sets of graphs that share certain
> characteristics, e.g. those required by some application.

A certain community has used shape in this way.  One of the contentious points 
in the formation of the working group was just what a shape meant.  Given that 
the working group is labelled as being about shapes, and there are people in 
the working group (myself included) who do not support this definition of 
shapes as applied to what the working group is supposed to be doing, I don't 
think that it is helpful to say that shapes are to be used this way.

A shape
> describes the expected contents of a graph. This includes expected arc
> labels, occurrence constraints, etc.
>
> The term "resource shape" is an abbreviation for the "shape of the graph
> of the RDF representation of an information resource".

Wow!  That's very different from what I thought that resource shapes was being 
used for by the resources shapes community.  I'm not even sure that this makes 
sense at all.


I'll put together a separate message about what I think this could mean and 
whether it makes sense to me at all.


> _________________________________________________________
> Arthur Ryman
> Chief Data Officer
> SWG | Rational
> 905.413.3077 (phone) | 416.939.5063 (cell)
> IBM InterConnect 2015
>
>
Received on Friday, 19 December 2014 04:32:22 UTC

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