[occi-wg] OCCI Model UML, XSD, XML, Code...

[Edmonds, AndrewX]

I've been spent some time on the proposed meta-model [1] and model [1] UML that is up on the wiki along with the inputs of others. Following some discussions with Roger and Andre, I decided to take the model in its UML form and create the corresponding XSD. In fact Roger might have the a RDF version of the XSD sometime. This XSD can be found here [2]. Now I don't class myself as a XSD expert so any comments, updates etc are appreciated. From this XSD I was able to generate an API to create and manipulate an in-memory representation of a model instance. This example code can be found here [3]. It's Java and uses XMLBeans[4], but there are many other libraries out there that will allow the generation of an API in languages such as Python[5], Ruby[6], CSharp[7] (typically any language that has SOAP libraries will have an XSD class generator). After rendering the in-memory model the XML rendering is specific but adheres to the OCCI model schema and can be viewed here[8]. Again how things appear in the XML can be tweaked via iteration of the schema. For those JSON peeps out there there's an already XSLT transform sheets out there that will convert this XML to JSON using different conventions [9][10].

This model is abstract in a sense it does not import any dependencies, such as Atom. @Sam perhaps you could take what I've done and either by way of model inheritance or composition show how Atom would integrate with this model?

My view on Atom is that it is useful as a wrapper to renderings of OCCI model instances. If I wanted to publish an OCCI model via Atom then I'd insert a model instance rendering into an atom:entry element (note we could include JSON via CDATA but this is where JSON perhaps gets a little ugly). This would be OCCI using Atom by way of composition and would allow both Atom and OCCI live harmoniously together or separately and not require Atom dependencies should that be the choice of a provider. What's important is that the OCCI model be it via Atom or something else could be understood by a receiving system. Using Atom with OCCI by way of inheritance makes the previous "with or without" approach a little more difficult as there's a hard-dependency on Atom.

Atom reminds me somewhat of WS-Agreement, SOAP etc. It doesn't solve your domain-specific model problems (i.e. what you are trying to represent - OCCI==Infrastructure), only provide a means to send this content about and mechanisms supporting this but perhaps not directly to the model contained as content. We still have to understand and represent our noun/verb/attribute triplets. Atom doesn't really help out bar the features it offers by way of sitting on top of HTTP. Now of course you can extend Atom base types (in fact AFAIK they're just xs:complexTypes W3C XSD types) but the point is you have to extend them to _something_. That something is your domain specific model. There is value however in Atom, not from the model point of view - it's a very simple model. The value in Atom is in the directions the specifications gives pertaining to Atom service behaviour. Another way to view Atom is the interoperability glue in between the now almost commonly accepted cloud stack of Infrastructure -> Platform -> Service. This is where OCCI could learn quite an amount but when you consider that the basis of these behaviours are steeply entrenched in REST design principles it's easy to see 1) why Atom is attractive 2) that you don't necessarily need Atom to have correct and/or standard service behaviour - just adopt good, sound REST design principles!

On more specifics and related to the attributes of each noun, we are still rather under-specified especially in the Storage and Network nouns. @Richard and @Gary (in separate threads) started a useful discussion on attributes for these nouns. Perhaps you two guys could add your findings and suggestions to the wiki?

Andy

PS: for those of you wanting to run the code I've exported the eclipse project and can be found here [11].

[1] http://forge.ogf.org/sf/wiki/do/viewPage/projects.occi-wg/wiki/NounsVerbsAndAttributes
[2] http://forge.ogf.org/sf/wiki/do/viewAttachment/projects.occi-wg/wiki/NounsVerbsAndAttributes/occi.xsd
[3] http://forge.ogf.org/sf/wiki/do/viewAttachment/projects.occi-wg/wiki/NounsVerbsAndAttributes/OCCITest.java
[4] http://xmlbeans.apache.org
[5] http://www.rexx.com/~dkuhlman/generateDS.html
[6] http://dev.ctor.org/soap4r/browser/trunk/bin/xsd2ruby.rb
[7] http://xsd2code.codeplex.com/Wiki/View.aspx
[8] http://forge.ogf.org/sf/wiki/do/viewAttachment/projects.occi-wg/wiki/NounsVerbsAndAttributes/occi-instance.xml
[9] http://code.google.com/p/xml2json-xslt/
[10] http://www.bramstein.com/projects/xsltjson/
[11] http://forge.ogf.org/sf/wiki/do/viewAttachment/projects.occi-wg/wiki/NounsVerbsAndAttributes/OCCIModel-eclipse-project.zip

Andy Edmonds
skype: andy.edmonds
tweets: @dizz
tel: +353 (0)1 6069232

IT Research - IT Innovation Centre - Intel Ireland Ltd.
Intel Ireland Limited (Branch)
Collinstown Industrial Park, Leixlip, County Kildare, Ireland
Registered Number: E902934

This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.


-------------------------------------------------------------
Intel Ireland Limited (Branch)
Collinstown Industrial Park, Leixlip, County Kildare, Ireland
Registered Number: E902934

This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.