[oslc-core] Meeting notes and using rdf:RDF as root element

[Arthur Ryman]

Dave,

I think we need to seriously re-examine our goals for defining a 
"simplified" subset of RDF/XML for OSLC specs. The latest change to using 
<rdf:RDF> as the document root now invalidates one of the original goals 
of making the content look like "normal" XML. Now it is very clear that 
the document is RDF/XML. Also, since we are using the content type 
application/rdf+xml it seems wrong for OSLC to define restrictions on the 
format.

The intended benefit for restricting the format was that it would allow 
implementers to reuse their XML parsing skills and tools. However, we are 
already using most of the RDF/XML syntax so writing an XML parser will 
require work. The easiest way to process RDF/XML is to use one of the many 
available RDF toolkits. These toolkits let you parse RDF documents into a 
triples data structure, modify the data, and write it back out again.

Suppose as an implementer I want to use an RDF toolkit. Now I need to do 
extra work to implement the OSLC subset. If I implement a service, am I 
obligated to throw an exception if the incoming RDF does not conform to 
the OSLC subset? If I don't then I am lulling the client into a false 
sense of security since if they access a different service implementation, 
it may be less forgiving. Furthermore, when I try to generate RDF using 
the toolkit, it will not conform to the OSLC subset so I'll have to write 
my own serializer. We are therefore in the paradoxical situation of 
embracing RDF as our data model yet making life more difficult for 
implementers that want to use RDF toolkits.

We started down the path of trying to make RDF look like "normal" XML in 
2009. That was based on our perceived market adoption of RDF. I supported 
that decision based on some negative customer reaction to RDF versus plain 
old XML. However, during the past year there has been a dramatic increase 
in the amount of RDF on the Web as part of the Linked Open Data movement. 
There is a lot of adoption by the USA and UK governments. I think in 2010, 
RDF is a much less risky technology.

The fact that we were led to using <rdf:RDF> as the root element, as well 
as using several other features of RDF/XML (e.g. blank node ids), should 
tell us that perhaps the features of RDF/XML are necessitated by the 
nature of the RDF data model itself, and that as we learn more, we'll be 
led to adopting more of RDF/XML syntax.  We can simplify the Core spec if 
we simply adopt RDF/XML as a specified by W3C. This is in line with our 
use of other RDF formats, such as Turtle.

One objection I heard was that RDF/XML would be hard to parse in a browser 
using Javascript. That same objection applies to the OSLC subset of 
RDF/XML. Our answer for the browser should be JSON, and by similar 
reasoning to the above, we should understand why we are not simply 
adopting one of the existing JSON encodings of RDF. e.g.from Talis. The 
potential advantage is the availability of toolkits for that encoding.

Could you include this topic on the agenda of our next workgroup meeting? 
Thx.

Regards, 
___________________________________________________________________________ 

Arthur Ryman, PhD, DE


Chief Architect, Project and Portfolio Management

IBM Software, Rational

Markham, ON, Canada | Office: 905-413-3077, Cell: 416-939-5063
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From:
Dave <snoopdave at gmail.com>
To:
oslc-core <oslc-core at open-services.net>
Date:
06/30/2010 02:58 PM
Subject:
[oslc-core] Meeting notes and using rdf:RDF as root element
Sent by:
oslc-core-bounces at open-services.net



I posted some notes on the Core meeting agenda page for today:
   http://open-services.net/bin/view/Main/OslcCoreMeetings20100630

One of the topics we discussed today was Link Guidance and the fact
that the proposed form for "link annotated with property-values"
requires <rdf:RDF> as the root element of OSLC Defined Resource
representations.

We discussed the impact of this change on implementations now
in-flight and those moving from v1 to v2 and agreed that this change
is late-breaking but not too late. If we wait a week, it may be too
late so we agreed to get this change in now and then socialize and
gather feedback.

The change is now in the Core spec draft as well as the RDF/XML and
Atom representation examples:
   http://open-services.net/bin/view/Main/OSLCCoreSpecDRAFT
   http://open-services.net/bin/view/Main/OSLCCoreSpecAppendixBDRAFT
   http://open-services.net/bin/view/Main/OSLCCoreSpecAppendixEDRAFT

Feedback is most welcome.

Thanks,
- Dave

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