Open Cloud Computing Interface

Cloud computing currently is covered by three models offering Infrastructure as a Service (IaaS), Platform as a Service (PaaS) and Software as a Service (SaaS), which all involve the on-demand delivery of computing resources.

There are a growing number of providers offering IaaS solutions for elastic capacity, whereby server “instances” are executed in their proprietary infrastructure and billed on a utility computing basis (typically virtual machines on a per instance per hour basis).

There are also a number of commercial and open source products which seek to replicate this functionality in-house while exposing compatible interfaces so as “hybrid cloud” operating environments can be created.

OCCI Working Group


The Open Cloud Computing Interface Working Group (OCCI-WG) within the Open Grid Forum (OGF) was founded during a BoF session at OGF25 in March 2009 by RESERVOIR partners Ignacio M. Llorente and Thijs Metsch (first named Cloud API (CAPI)).

Since then, they have played a major role in providing a lightweight, interoperable Application Programming Interface (API) to access and manage Cloud computing Infrastructures exposed as a Service, or IaaS for short. The API specification for remote management of cloud computing infrastructure will lead to the development of interoperable tools for common tasks including deployment, autonomic scaling and monitoring and, in particular, will allow:

  • Consumers to interact with cloud computing infrastructure on an ad-hoc basis (e.g. deploy, start, stop, restart)
  • Integrators to offer advanced management services
  • Aggregators to offer a single common interface to multiple providers
  • Providers to offer a standard interface that is compatible with available tools
  • Vendors of grids/clouds to offer standard interfaces for dynamically scalable service delivery in their products

The requirements

Use cases considered by OCCI Working Group have highlighted a number of specific requirements for IaaS.

  • One such requirement is the need for “machine-readable” Service Level Agreements (SLAs) associated with the dynamic provisioning of Cloud computing resources.
  • A second requirement is the need for service managers enabling the detailed management of Cloud instances and their attributes.
  • The possibility of creating web-based front-ends calling the OCCI API to instantiate and manage Cloud computing resources is another core requirement.

Finally, there is a need for a scriptable, RESTful API capable of provisioning, executing and monitoring tasks.

OCCI documents available on the OGF website:

  • Use cases and requirements for a Cloud API – final [link]
  • Technical specification of the Open Cloud Computing Interface API – draft
  • OCCI Charter