This document, part of a document series produced by the OCCI working group within the Open Grid Forum (OGF), provides a high-level definition of a Protocol and API. The document is based upon previously gathered requirements and focuses on the scope of important capabilities required to support modern service offerings.
 
The Open Cloud Computing Interface (OCCI) is a RESTful Protocol and API for all kinds of management tasks. OCCI was originally initiated to create a remote management API for IaaS1 model-based services, allowing for the development of interoperable tools for common tasks including deployment, autonomic scaling and monitoring. It has since evolved into a flexible API with a strong focus on interoperability while still offering a high degree of extensibility. The current release of the Open Cloud Computing Interface is suitable to serve many other models in addition to IaaS, including PaaS and SaaS.
 
In order to be modular and extensible the current OCCI specification is released as a suite of complementary documents, which together form the complete specification. The documents are divided into four categories consisting of the OCCI Core, the OCCI Protocols, the OCCI Renderings and the OCCI Extensions.

• The OCCI Core specification consists of a single document defining the OCCI Core Model. OCCI interaction occurs through renderings (including associated behaviors) and is expandable through extensions.
• The OCCI Protocol specifications consist of multiple documents, each describing how the model can be interacted with over a particular protocol (e.g. HTTP, AMQP, etc.). Multiple protocols can interact with the same instance of the OCCI Core Model.
• The OCCI Rendering specifications consist of multiple documents, each describing a particular rendering of the OCCI Core Model. Multiple renderings can interact with the same instance of the OCCI Core Model and will automatically support any additions to the model which follow the extension rules defined in OCCI Core.
• The OCCI Extension specifications consist of multiple documents, each describing a particular extension of the OCCI Core Model. The extension documents describe additions to the OCCI Core Model defined within the OCCI specification suite.

The current specification consists of seven documents. This specification describes version 1.2 of OCCI and is backward compatible with 1.1.
 
This document presents the text-based renderings. To be complaint, OCCI implementations MUST implement the three renderings defined in sections 6, 7 and 8.
The following specification of the text-based renderings is in the process of being deprecated and will be removed or significantly changed in the next MAJOR release of the standard.
The document is structured by defining base ABNFs, which can then be combined into renderings, which will be rendered over a protocol (e.g., HTTP) by the specific rendering definitions.