[occi-wg] RDF, RDFa and HTML
Edmonds, AndrewX
andrewx.edmonds at intel.com
Thu Jun 24 11:20:36 CDT 2010
Hey Gary :-)
Responses inline...
-----Original Message-----
From: Gary Mazz [mailto:garymazzaferro at gmail.com]
Sent: Thursday, June 24, 2010 4:27 PM
To: Edmonds, AndrewX
Cc: Roger Menday; occi-wg
Subject: Re: [occi-wg] RDF, RDFa and HTML
Hi,
I have a couple of issues, I'm going to be terse, I don't have a lot of
time today.
1) There are a couple of RDF initiatives to directed at fostering reuse
and management of vocabularies; Dublin Core's DCMI and the Ontology
Metadata Vocabulary (OMV). I'm not sure if they are mutually exclusive,
complimentary or if they are interoperable. We need to determine the
impact to our work. Maybe Roger Menday can help clarify ?
There's plenty of sense in investigating this. One thing to be weary of is introducing dependencies on classes, attributes etc that are RDF specific. We still need to support HTTP Headers.
2) We need to take a close look at the html's RDFa's mapping. We should
try to eliminate as much overlap as possible between elements and
attributes that are already defined html and especially the items that
affect browser renderings. See number 4 below
I can't quite see what the issue is here yet. Can you give an example of overlaps in the examples?
3) We need to decide whether the RDFa content is visible to browsers or
we use JS to access RDFa elements and attributes. I had initially
decided to make the RDFa invisible and use JS to reference information
needed to be rendered. If we allow direct rendering, we will need to
implement item list as number 4.
Ah yes, I've another mail coming on this more so related on write-class operations using RDFa as a payload. In the example RDFa I sent values are exposed in 2 different but compliant ways; using the 'content' RDFa attribute, in which case it's visually not displayed in web browsers. The second fashion places the value pointed to by the predicate as the literal value of the enclosing HTML element. I would lean towards the latter right now.
4) We also need to decide on the approach take to indicate relationships
between occi objects. RDFa will allow a server to project one or more a
occi graphs in a document or reference graphs across documents. Graphs
may not be top down. We need a way to represent the references and type
of relationship between graph elements. I was using the rel, rev, and
href to indicate relationships between information elements and the
backbone of decoupled graphs. Today, none of these attributes impact the
rendering of content in browsers
Relationships between OCCI instances are defined by the Link entity right? There was an example in the HTML files I sent around. Can you send an example of how you were doing it to compare?
Although in certain areas we are back fitting RDFa mapping into the RDF
vocabulary, I don't see a way to RDFa without remapping the RDF to RDFa
vocabulary.
Lost me there :-) Can you give me a concrete example to illustrate?
cheers,
gary
Edmonds, AndrewX wrote:
> You are more than welcome!
>
> Just a little note:
> The Link entity is incorrectly modeled for those that have checked things out there's a bunch of attributes hanging off it. They should not. I'll update the python and owl files when committing to svn (2xTODOs)
>
> Andy
>
> -----Original Message-----
> From: Roger Menday [mailto:roger.menday at uk.fujitsu.com]
> Sent: Thursday, June 24, 2010 11:53 AM
> To: Edmonds, AndrewX
> Cc: occi-wg
> Subject: Re: [occi-wg] RDF, RDFa and HTML
>
>
> hi Andy
>
> thanks for posting this. I'm digesting (and I hope others are too).
> I am very interested in seeing where OCCI can go with this - I hope to
> get back to you soon.
>
> Roger
>
> On 23 Jun 2010, at 12:44, Edmonds, AndrewX wrote:
>
>
>> Hi all,
>>
>> I've been looking into how OCCI can expose itself through a HTML
>> serialization and to demarcate machine readable, semantic content.
>> To demarcate that content we already decided that we would use RDFa
>> [1]. In order to truly and correctly use RDFa we need to be able to
>> point to the ontology (model) in which subject, predicate and object
>> triplets are defined. Defining the ontology is somewhat easy, we
>> have it already with the OCCI model; it's just a matter of
>> expressing it in RDF. With an ontology in hand, we can define
>> semantically marked-up HTML with the ontology's vocabulary using the
>> facilities of RDFa. I've worked on 2 ways of expressing the OCCI
>> model in RDF.
>>
>> 1. Using python [2].
>> 2. Using a modeling tool (Protégé) [3][4][5]. Note these owl files
>> may need their imports modified in Protégé.
>>
>> The only difference in the two is that occi.owl (core spec), occi-
>> infrastructure.owl (infrastructure spec) and occi-sla-at-soi.owl
>> (SLA at SOI extensions) are defined in separate files with the Protégé
>> approach. This should give folks an idea of how extensions for OCCI
>> can be introduced. However in both examples, occi-core, occi-
>> infrastructure and slasoi-infrastructure are separated by namespace.
>>
>> As RDFa does not explicitly define a rigorous structure for HTML
>> documents, and it shouldn't, we need to be able to express 2 basics
>> forms:
>>
>> 1. A concrete OCCI Kind instance (Compute, Storage, Network). I have
>> an example here [6].
>> 2. A collection of OCCI Kind instances. I have an example here [7].
>> In this example values of objects are exposed using the 'content'
>> RDFa attribute [8].
>>
>> Each example may not be 100% perfect but what's most interesting is
>> when you run the each HTML rendering through a RDFa parser [9]
>> (examples here [10] [11]). The RDF extracted is quite along the
>> lines of what some might expect an OCCI POX format to be. Note, I'm
>> not advocating POX, just pointing to the flexibility of RDFa. There
>> are still some aspects to be worked out but I will follow up on
>> these in a separate mail (this one is long enough!).
>>
>> If you want to see how all of this visually looks then see here:
>> ontology only [12], ontology and graph instance [13].
>>
>> I'd really appreciate and love to hear people's comments, opinions
>> on this! :-)
>>
>> Andy
>>
>> [1] http://www.w3.org/TR/rdfa-in-html/
>> [2] http://dl.dropbox.com/u/165239/occi-rdf.py
>> [3] http://dl.dropbox.com/u/165239/occi.owl
>> [4] http://dl.dropbox.com/u/165239/occi-infrastructure.owl
>> [5] http://dl.dropbox.com/u/165239/occi-sla-at-soi.owl
>> [6] http://home.edmonds.be/occi-html5-rdfa-one.html
>> [7] http://home.edmonds.be/occi-html5-rdfa-list.html
>> [8] http://www.w3.org/TR/2010/WD-rdfa-core-20100422/#s_syntax
>> [9] http://www.w3.org/2007/08/pyRdfa
>> [10] http://www.w3.org/2007/08/pyRdfa/extract?uri=http%3A%2F%2Fhome.edmonds.be%2Focci-html5-rdfa-one.html
>> [11] http://www.w3.org/2007/08/pyRdfa/extract?uri=http%3A%2F%2Fhome.edmonds.be%2Focci-html5-rdfa-list.html
>> [12] http://dl.dropbox.com/u/165239/occi-rdf-graph-rev2.png
>> [13] http://dl.dropbox.com/u/165239/occi-rdf-graph-inst-rev2.png
>>
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>
>
> Roger Menday (PhD)
> <roger.menday at uk.fujitsu.com>
>
> Senior Researcher, Fujitsu Laboratories of Europe Limited
> Hayes Park Central, Hayes End Road, Hayes, Middlesex, UB4 8FE, U.K.
> Tel: +44 (0) 208 606 4534
>
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