JULY/AUGUST 2012 1089-7801/12/$31.00 © 2012 IEEE Published by the IEEE Computer Society 15 Programmatic Web Interfaces A ny attempt to standardize the inter- faces of commercial IT service offer- ings must cope with the tension between unification and differentia- tion. Although, from the standardiza- tion viewpoint, the agreed-on interface should be alike for all service provid- ers, each vendor naturally strives for a way to expose its unique features and ensure customer retention. In the domain of cloud computing, several current projects aim to provide a single API for the plethora of proprietary service provider interfaces. However, the most popular of these — libcloud (http://libcloud.apache.org) and Delta- Cloud (http://deltacloud.apache.org) — follow a proxy/adapter pattern approach. This has a fundamental limitation: it introduces an additional layer of indi- rection into the system. The Open Cloud Computing Interface (OCCI) addresses both the unifcation and differentiation aspects. It provides a unifed and extensible API and offers discoverable capabilities. OCCI reduces the overhead of code and operational management by removing intermedi- ate state management and reclaiming latency losses. Here, we describe OCCI’s development and architecture, discuss current issues associated with the spread of proprietary cloud manage- ment APIs and approaches to harmo- nize them, and highlight current OCCI implementations and deployments in the cloud community. Why a Cloud Standard? Multiple cloud service and software providers exist, and they all have some kind of API. So why do we need another one? We could have asked the same question about network software APIs before TCP became widely accepted as a lingua franca for networking. The answer at the time was that customers wanted to be able to buy from any ven- dor, possibly several at once, without Today’s cloud ecosystem features several increasingly divergent management interfaces. Numerous bridging efforts attempt to ameliorate the resulting vendor lock-in for customers. However, as the number of providers continues to grow, the drawback of this approach becomes apparent: the need to maintain adapter implementations. The Open Cloud Computing Interface builds on the fundamentals of modern Web-based services to defne a standardized interface for cloud environments while enabling service providers to differentiate their service offerings at the same time. Andy Edmonds Intel Labs Europe Thijs Metsch Platform Computing Alexander Papaspyrou Technische Universität Dortmund Alexis Richardson VMware Toward an Open Cloud Standard