OCCI and OpenStack

OpenStack is one of the major players in the cloud community at the moment. Still it currently lacks an standardized Interface which can be used to manage VMs. This changes now! During the Cloud Plugfest OCCI has been demoed on top of OpenStack.

The blueprint (details on wiki) for this feature enhancement has been around a while now. And based on this blueprint a first implementation has been created.

Andy Edmonds presented the following slides during the Cloud Plugfest in Düsseldorf which highlight more details of the OCCI interface for OpenStack

As noted this work has partly been sponsored by dgsi and FI-WARE. Now on to interoperability testing and looking into getting other Standards like CDMI on top of OpenStack.

Grokking OCCI Syntax: OCCI ANTLR Grammar

Interoperability is key belief in OCCI. The OCCI specifications set out in text how to implement the API and formats, however it is still up to our community and adopters to implement this. It is often the case when implementing a specification certain implementation decisions made can have an impact on an implementations interoperability. It is for this reason why this ANTLR grammar has been created (thanks to SLA@SOI) to aid developers in creating their parser. The ANTLR grammar specifies the text rendering format in an abstract language known as a grammar.


The grammar defined, when used with the ANTLR tools, will generate a lexer and parser that will validate any valid OCCI text format. The grammar itself does not currently check whether a value associated with an attribute is valid. Rather it primarily ensures that the structure of the request is valid. It is still up to the implementer that service behaviours (e.g. correctly responding to HTTP GETs) are implemented correctly.


One of the key strengths of ANTLR, outside of its lexer/parser technology, is it has a wide range of target languages (18), so your favourite language has a good chance!  This is an important advantage as this enables multiple implementations of OCCI (client or server) to all share a the same rules that parse the OCCI text format, regardless of language.

The Goodies

There are two grammars currently defined, one based on the other:

  1. occi-antlr-grammar: this solely defines the grammar and does not contain any target language specifics. It can be used as the foundation of target language specific OCCI grammars. An example of this extension is the occi-antlr-java. This grammar can generate lexer and parsers, however they will only validate the input and not extract values from the supplied input. If extracted values are required, a very common case, then the occi-antlr-java grammar gives an example of this.
  2. occi-antlr-java: this extends occi-antlr-grammar to include target language specifics. The target language used is Java. In this grammar file there are Java-specific ANTLR actions that extract the values from a valid OCCI text request/responses.
  3. occi-antlr-ruby: this just like occi-antlr-java extends the occi-antlr-grammar to include ruby language specifics. This was contributed by GWDG.

There are a number of rules that are present within the OCCI grammar that can be reused in order to validate certain supplied values. This would describe a second pass parsing phase. In the case that an implementer would like to validate a URI value then they can do so by using this URI grammar.

The following presentation also goes through some details related to ANTLR and the OCCI grammar.

We hope you find this useful! If there are any problems, issues or suggestions open a ticket.

OCCI HTTP Rendering Spec Released

The OCCI HTTP Rendering specification defines how to interact with the OCCI Core Model using the RESTful OCCI API. The document defines how the OCCI Core Model can be communicated with and thus serialised using the HTTP protocol via RESTful semantics.

This is the last document in the v1.1 document series and is now available on the main OGF web site as document GFD.185.

Thanks to all that contributed content and reviews!


OCCI Core & Models and Infrastructure documents released

Dear OGF Board and WG participants:

We would like to inform you that the Open Cloud Computing Interface Core & Models and Infrastructure specification documents, GFD.183 and GFD.184, were published today as OGF Proposed Recommendations and are now available for downloading on the http://ogf.org/documents site.

We are very proud of all of the accomplishments of all OGF work groups and of the entire OGF document series. Thank you for all of your work, regardless of the work group or area in which you are making contributions.

OCCI represents the work of a dedicated set of participants that deserves highlighting, however, and that opens up a significant set of opportunities for new work in OGF in the area of cloud computing. Here for your information is some of the text that we have been using in announcing the release of the first two documents in the series. The next document covering the HTTP rendering just completed its public comment period and should be completed and ready for publication shortly.

OCCI is a general-purpose set of specifications for cloud-based interactions with resources in a way that is explicitly vendor-independent, platform-neutral and can be extended to solve a broad variety of problems in cloud computing. The OCCI specification set is a product of the Open Grid Forum. OGF is a leading development organization for open standards in the area of distributed networking, computing and storage with an emphasis on technologies for large-scale distributed computing. OGF develops its standards through an open process that gathers input and contributions from the community and refines them through peer review and public comment to produce standards, guidance and information of value to the community through the Grid Final Document (GFD) series.

We are very proud of OCCI and think that it provides an important and timely set of contributions to cloud computing technology that is already gathering great interest and rapid evidence of adoption by a broad range of participants in the cloud computing community.

Congratulations to the OCCI working group and its participants. More information can be found on the OGF and OCCI working group sites at http://ogf.org and http://occi-wg.orgrespectively. Please let me know if you have any further questions.

Alan Sill
VP of Standards
Open Grid Forum

Source.: http://www.ogf.org/pipermail/wg-all/2011-April/000313.html

OCCI 1.1 Document Series in Public Comment

As of today, all the documents for the revised version (1.1) of the OCCI document series are now in public comment. A lot of work by the OCCI community has gone into this revision so a huge “thanks!” goes out to all who have contributed to the many discussions on the mailing list, IRC, wiki and confcalls. This version paves the way to much exciting implementation work and plugfests in the upcoming months. If you would like to make comments and have your views heard and taken on board, now is an excellent time to do so. Simply:
  1. navigate to the public comments section on the OGF website,
  2. grab a copy of any or all the specification documents
  3. read the spec
  4. submit any comments, questions or improvements back to the public comments page (this can be anonymous if you prefer)

OCCI Compliance Testing Tool

The OCCI working group is happy to announce the availability of a test tool to verify OCCI implementations compliance with OCCI 1.1. Though still in development, we would really like to share this with the community and ask for help to extend the test and verify the test code.

Note: do be careful when examining the output of the tool, as a quote of Edsger W. Dijkstra (not to mention Heisenburg) states:

Program testing can be used to show the presence of bugs, but never to show their absence!

The following screenshot shows the GUI of the test tool (it also runs from the command line):

The source code can be found in the GridForge Source Code Repository. If you have any suggestions or comments let us know through the usual channels!