OCCI is a boundary protocol and API that acts as a service front-end to a provider’s internal management framework by exposing its resources. As of this writing (early 2015) the specification consist of three documents.

• OCCI Core describing the formal definition of the the OCCI Core Model
• OCCI Infrastructure defining the OCCI Infrastructure extension for the IaaS domain, defining additional resource types, their attributes and the actions that can be taken on each resource type
• OCCI HTTP Rendering defining interaction with the OCCI Core Model using the RESTful OCCI API

The OCCI Working Group is also working on additional specification, currently in various stages of progress:

• OCCI XML Rendering
• OCC JSON Rendering
• OCCI Billing and Monitoring
• OCCI PaaS extension
• OCCI SLAs extension

Standard implementation status overview is maintained at: http://occi-wg.org/community/implementations/