RE: Shapes, Individuals, and Classes - OSLC Motivations

Irene,

The triple "project1:customerReference rdfs:domain oslc_cm:ChangeRequest" 
is not a constraint. It is an inference rule that states if you have a 
triple "X project1:customerReference Y" then you can infer a triple "X 
rdf:tytpe oslc_cm:ChangeRequest".

What we want in the OSLC use case is for the web application that hosts 
the resources that belong to project1 to advertise the fact there is a new 
property "project1:customerReference", which is an extension to the OSLC 
CM specification. This is allowed by the OSLC CM specification since it 
specifies an open content model. A resource of type oslc_cm:ChangeRequest 
is allowed to have properties not defined by the OSLC CM specification.

OSLC adopts the design principles of Linked Data. Roughly, this is REST + 
RDF. OSLC does not depend on RDFS or OWL terms that require inferencing. 
OSLC does provide vocabulary documents using RDFS and OWL annotation 
terms. A compliant OSLC implementation does not require an RDFS or OWL 
reasoner. This choice was made in order to lower the implementation burden 
for existing web applications to provide Linked Data interfaces. 

As far as OSLC is concerned, rdf:type is simply another property. It has 
no OO connotations. The RDF representation of an HTTP resource is simply a 
set of triples. The URI of the resource itself will normally be the 
subject node of many of the triples and it will normally have one or more 
rdf:type triples.

In the world of Linked Data, it does not make sense for project 1 to have 
its own definition of oslc_cm:ChangeRequest since oslc_cm:ChangeRequest is 
a URI that belongs to the OSLC URI space. To get authoritative information 
about oslc_cm:ChangeRequest, you do an HTTP GET on it. That request will 
return its RDFS vocabulary document, which is hosted on the OSLC server. 
OSLC defines the meaning of the terms in its URI space. Other applications 
are encouraged to reuse those terms if their use is consistent with the 
OSLC definition. In order to make terms widely reusable, OSLC avoids this 
use of RDFS terms such as rdfs:domain and rdfs:range since they may entail 
undesired inferences.

_________________________________________________________
Arthur Ryman
Chief Data Officer
SWG | Rational
905.413.3077 (phone) | 416.939.5063 (cell)
IBM InterConnect 2015




From:   "Irene Polikoff" <irene@topquadrant.com>
To:     Arthur Ryman/Toronto/IBM@IBMCA, "'Peter F. Patel-Schneider'" 
<pfpschneider@gmail.com>, 
Cc:     <public-data-shapes-wg@w3.org>
Date:   11/06/2014 05:43 PM
Subject:        RE: Shapes, Individuals, and Classes - OSLC Motivations



Sorry, I meant project1:customerReference rdfs:domain 
oslc_cm:ChangeRequest

-----Original Message-----
From: Irene Polikoff [mailto:irene@topquadrant.com] 
Sent: Thursday, November 06, 2014 4:25 PM
To: 'Arthur Ryman'; 'Peter F. Patel-Schneider'
Cc: public-data-shapes-wg@w3.org
Subject: RE: Shapes, Individuals, and Classes - OSLC Motivations

< For example, one project might add a customer reference number while
another might add a boolean flag indicating if there is an impact to the
online documentation. These custom attributes also appear as additional 
RDF
properties of the resources.

OSLC specifications typically define one or more RDF types. For example, 
the
RDF type for change requests is oslc_cm:ChangeRequest where the prefix
oslc_cm is <http://open-services.net/ns/cm#>. The RDF representation of an
OSLC change request contains a triple that defines its type as
oslc_cm:ChangeRequest, triples that define RDF properties as described in
the OSLC CM specification, and additional triples that correspond to
tool-specific or project-specific custom attributes. 

Note that the addition of custom attributes does not require the 
definition
of a new RDF type. Furthermore the RDF properties used to represent custom
attributes may come from any RDF vocabulary. In fact, tool administrators
are encouraged to reuse existing RDF properties rather than define
synonyms.>

Then, members of oslc_cm:ChangeRequest for project 1 must have a property
project1:customerReference and for project2, members of this class have a
property project2:documentationImpact.

Such extensions of some core ontology(s) are pretty common. One may decide
to create a project1:ChangeRequest class for this or simply add a triple
oslc_cm:ChangeRequest rdfs:domain project1:customerReference to the graph
that contains the ontology used for project 1. Which of these approaches 
to
use is a matter of preference/implementation.

I do not see a problem or any special requirement here. It is "business as
usual". Am I missing something?

Irene

-----Original Message-----
From: Arthur Ryman [mailto:ryman@ca.ibm.com]
Sent: Thursday, November 06, 2014 3:02 PM
To: Peter F. Patel-Schneider
Cc: public-data-shapes-wg@w3.org
Subject: Re: Shapes, Individuals, and Classes - OSLC Motivations

Peter,

I've created a user story [1] that describes "custom attributes" and 
related
concepts. These concepts were not created by OSLC. Rather, OSLC was 
designed
to accommodate this situation which is very common in software development
tools and probably many other applications.

For example, consider GMail Contacts. It defines several types of phone
number (home, work, mobile), address (home, work), etc, but you can add
custom types. You'd probably start with vCard as the RDF representation. 
Now suppose your company was using GMail, and that you could configure it
with some additional types of phone number, and could specify the RDF
property for those.

[1]
https://www.w3.org/2014/data-shapes/wiki/User_Stories#S24:_Open_Content_Mode

l
_________________________________________________________
Arthur Ryman
Chief Data Officer
SWG | Rational
905.413.3077 (phone) | 416.939.5063 (cell) IBM InterConnect 2015




From:   "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
To:     Arthur Ryman/Toronto/IBM@IBMCA, 
Cc:     public-data-shapes-wg@w3.org
Date:   11/06/2014 12:14 PM
Subject:        Re: Shapes, Individuals, and Classes - OSLC Motivations



I still don't know what "custom" means here with respect to RDF.  As far 
as
I can tell any bit of an ontology, or class, or property, or constraint, 
or
shape could be called "custom".  Now it may be that within OSLC there is
some notion of custom vs non-custom, but how can that notion be removed 
from
OSLC so that it can be used elsewhere?

Similarly, the notions of "specification", "implementation", "project",
etc., appear to me to be specific to OSLC, and particular to the design
methodology you outline below, and using them to drive a spec could, I
think, tie that 

spec quite closely to the design methodology.



As a contrast, here is what I believe should be used to say that classes 
and
shapes/constraints are decoupled.

Definition:  Classes and shapes/constraints are decoupled if the
specification can use different sets of shapes/constraints on the same
class.  For example, if the specification permits the ontology
   ex:Person rdf:type rdfs:Class .
   ex:name rdf:type rdf:Property .
   ex:name rdfs:domain ex:Person .
to be used with the constraint set
   ex:Person < exists ex:name
(every person has a "known" value for its name) or used with the 
constraint
set
   ex:Person < all ex:name xsd:string
(all "known" names of people are strings) then it will be said to allow 
the
decoupling of constraints/shapes and classes.


A stronger notion would be that shapes/constraints are independent of
classes. 
  This could be defined as:

Definition:  Classes and shapes/constraints are independent if some
shapes/constraints do not use class membership in their definition.  For
example, the following constraint is class-independent:
   exists ex:name < exactly 1 ex:name
(if something has a "known" name then it has exactly one "known" name)


peter




On 11/06/2014 04:59 AM, Arthur Ryman wrote:
> Peter,
>
> OSLC defines specification for RDF representation of resources in
several
> domains, e.g. Requirements, Quality, Change Management etc. A 
> specification typically defines a class and several properties.
> Implementations are allowed to add new RDF properties but they don't 
> necessarily introduce new RDF classes. Furthermore, within an 
> implementation, users may add custom RDF properties on a 
> project-by-project basis, but that doesn't change the RDF class.
Therefore
> different projects use different Shapes but the Shapes only differ by
RDF
> properties, not RDF classes. That is what I mean by decoupling Shapes
and
> Classes.
>
> I will elaborate this on the wiki.
> _________________________________________________________
> Arthur Ryman
> Chief Data Officer
> SWG | Rational
> 905.413.3077 (phone) | 416.939.5063 (cell) IBM InterConnect 2015
>
>
>
>
> From:   "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
> To:     Arthur Ryman/Toronto/IBM@IBMCA, public-data-shapes-wg@w3.org,
> Date:   11/05/2014 05:27 PM
> Subject:        Re: Shapes, Individuals, and Classes - OSLC Motivations
>
>
>
> I'm still wondering what you think it means to decouple shapes and
> classes.
> The first motivation you provide is supported by both SPIN and OWL
> constraints.  I can't figure out what custom properties have to do with
> classes, or constraints, or shapes.  The behaviour you appear to be
> looking
> for in your second paragraph is also supported by both SPIN and OWL
> constraints.
>
> I had thought that this was ironed out at the Face-to-Face, but I guess
> not.
>
> peter
>
>
> On 11/05/2014 01:47 PM, Arthur Ryman wrote:
>> There are a few motivations for decoupling shapes and classes. One is
> that
>> the creation shape may be different than the update shape. Another has
> to
>> do with custom properties. I'll write up the following in the wiki.
>>
>> OSLC supports an open content model for resources. It is common for
> tools
>> to add their own custom properties, and for projects within a tool to
> have
>> different user-defined properties. For example, consider a bug tracking
>> tool. Project A may add a custom property foo and project B may add 
bar.
>> All projects use the same RDF type for bug resources, e.g.
>> oslc_cm:ChangeRequest. However, the shape for resources in project A
>> differs for the shape for project B.
>> _________________________________________________________
>> Arthur Ryman
>> Chief Data Officer
>> SWG | Rational
>> 905.413.3077 (phone) | 416.939.5063 (cell)
>> IBM InterConnect 2015
>>
>>
>
>
>

Received on Tuesday, 11 November 2014 21:30:25 UTC