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Re: shapes-ISSUE-18 (S35 examples): S35 needs to state what constraints are required

From: Arthur Ryman <ryman@ca.ibm.com>
Date: Thu, 8 Jan 2015 16:08:40 -0500
To: RDF Data Shapes Working Group <public-data-shapes-wg@w3.org>
Message-ID: <OFD7021135.5EAC9D6F-ON85257DC7.0072DB5A-85257DC7.007426E2@ca.ibm.com>
I added the following text to the wiki:

Some of the proposed solutions (Resource Shapes, ShEx, SPIN) appear to 
have an implicit assumption that the only RDF graphs of interest to this 
workgroup are like programming language data structures in the sense that 
there is a distinguished root node which is the subject of triples that 
define either literal properties or links to other subjects, which may in 
turn have literal properties or links to further subjects, or so forth. 
The implication is that all the nodes of interest are connected to the 
root node. Therefore, these proposals are incapable of describing 
disconnected graphs. The point of this user story is to provide evidence 
that disconnected graphs are of interest. It also attempts to make the 
point that the output of this workgroup should be applicable to general 
RDF graphs and not just some subset of graphs that follows some popular 
design pattern. 
The example is taken from a specification related to access control. A 
conformant access control service must host an access control list 
resource that supports HTTP GET requests. The response to an HTTP GET 
request have a response body whose content type is application/ld+json, 
i.e. JSON-LD. An example is given below. In this example, there is a 
distinguished root node, i.e. the node of type acc:AccessContextList, but 
it is not connected to the other nodes of interest, i.e. the nodes of type 
acc:AccessContext. 
An informal specification for valid RDF graphs is as follows: "Let X be 
the URI of an access control list information resource. Its RDF graph must 
must contain X as a resource node. X must have type acc:AccessContextList. 
X must have a string-valued dcterms:title property and a string-valued 
dcterms:description property. In addition, the graph may contain zero or 
more other resource nodes (URIs) of type acc:AccessContext. Each of these 
other nodes must have a string-valued dcterms:title property and a 
string-valued dcterms:description property. The graph may contain other 
triples." 
This user story does not propose that a shape language must be able to 
distinguish between connected and disconnected graphs. 
_________________________________________________________
Arthur Ryman, PhD
Distinguished Engineer | Master Inventor | Academy of Technology
Chief Data Officer
SWG | Rational
905.413.3077 (phone) | 416.939.5063 (cell)
IBM InterConnect 2015


"RDF Data Shapes Working Group Issue Tracker" <sysbot+tracker@w3.org> 
wrote on 12/18/2014 11:01:08 PM:

> From: "RDF Data Shapes Working Group Issue Tracker" 
<sysbot+tracker@w3.org>
> To: public-data-shapes-wg@w3.org
> Date: 12/18/2014 11:01 PM
> Subject: shapes-ISSUE-18 (S35 examples): S35 needs to state what 
> constraints are required
> 
> shapes-ISSUE-18 (S35 examples): S35 needs to state what constraints 
> are required
> 
> http://www.w3.org/2014/data-shapes/track/issues/18
> 
> Raised by: Peter Patel-Schneider
> On product: 
> 
> S35 https://www.w3.org/2014/data-shapes/wiki/
> User_Stories#S35:_Describe_disconnected_graphs talks about 
> constraints over disconnected graphs.  However, it does not state 
> why disconnected graphs are different from connected graphs?  Are 
> the constraints supposed to recognize disconnected graphs?  Or are 
> the constraints just supposed to work on disconnected graphs, and 
> what differences in constraint handling are required for disconnected 
graphs.
> 
> SPIN and OWL constraints don't care whether a graph is connected or 
> disconnected.
> 
> 
> 
Received on Thursday, 8 January 2015 21:09:09 UTC

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