Microsoft has joined the Open Data Center Alliance, a user-led organization that aims to simplify the purchasing of data center and cloud services by promoting interoperability and common standards.

The alliance has gathered over 300 members in its two-and-a-half years of existence. Most of them are users of data center and cloud services: Banks and telcos dominate, but others include a U.S. university, a French car manufacturer and the Dutch national police agency.

Vendors are welcome to join too, either as solution provider members or, like Microsoft, as contributor members, a status that allows them to see early drafts of the organization's publications and to contribute to the technical workgroups that write them.

Those publications include "usage models" defining standard terminology to aid in the writing of requests for proposals. The usage models cover areas including service orchestration, secure federation, long-distance workload migration and interoperability across clouds. There is also a tool to help write RFPs. The Proposal Engine Assistant Tool (PEAT) can generate ODCA-recommended verbiage calling for open, standards-based solutions to a variety of requirements.

Mario Mueller, ODCA Chairman and also vice president of IT infrastructure at BMW, welcomed Microsoft's move.

"Microsoft has a lot of experience in the cloud environment, especially in open standards and interoperability," Mueller said. "In the ODCA, we collaborate on the development of interoperability standards."

For Microsoft, membership of the ODCA will open up another forum where it can connect with users of its Azure cloud platform and services, said Colin Nurse, the company's CTO for global accounts. "Listening to customers is always a good thing for the industry to do," he said.

That's a sentiment echoed by Laurent Lachal, senior analyst for cloud computing research at Ovum.

"A lot of the large accounts that Microsoft has are in the ODCA, and it needs to follow them," he said.

Nurse said the alliance's emphasis on interoperability is important too.

"We're pretty proud of the interoperability of our Azure services," he said, emphasizing the broad range of protocols and non-Microsoft languages that Azure supports, including PHP and Python in addition to Microsoft's own .Net.

It's not just about interoperability between applications running in the cloud, though: It's also about the interoperability of the underlying infrastructure, and the ability to move workloads around.

"We do have customers that offer services across multiple cloud vendors, including us, because you don't want to put all your eggs in one basket," he said.

Other cloud vendors have already joined the ODCA, including Capgemini, Rackspace, Savvis and Verizon Terremark, but two big players are absent: Amazon Web Services, and Google with its App Engine, Cloud Storage and BigQuery services.

That's understandable, said Ovum's Lachal, because those vendors already in the ODCA are focused on large companies, and understand the constituency that makes up the ODCA, while AWS and Google are not natural participants.

"I see interaction with ODCA members as more of a top-down kind of thing, whereas AWS and Google are more of a bottom-up thing," he said. ODCA can be prescriptive and slow, whereas AWS and Google are more fast-moving.

"As ODCA gains more momentum, and as Google and Amazon move up the enterprise food chain, there may be more convergence," he said.