Amazon and Microsoft--both of which declined to sign the newly published Open Cloud Manifesto--yesterday said they won't lock customers into their respective cloud services.Their comments were made in separate presentations at the Cloud Computing Expo in New York. In the opening keynote, Amazon CTO Werner Vogels said customers can "mix and match" Amazon Web Services with cloud services from other vendors because Amazon exposes its services as "standard interfaces." Users of Amazon's Elastic Compute Cloud, for example, aren't limited to Amazon's Simple Storage Service as their data-storage option. "You can use EC2 and storage services from another party," Vogels said. "There is no lock-in."

Vogels referred to IBM, Microsoft, Oracle, Red Hat, Sun, and Salesforce as partners, noting that their software is available as on-demand, virtualized instances on EC2. He highlighted platform-as-a-service provider Stax Networks--which hosts its service on EC2--as an example of the heterogeneous nature of Amazon's cloud. Stax Networks lets users develop and deploy Java applications on EC2. "This demonstrates that you can go up the [software] stack and still be fully open," he said.

A bit later, Microsoft distinguished engineer Yousef Khalidi gave an update on Microsoft's Azure cloud services. Khalidi said Azure, which is in pre-beta testing, is "designed for interoperability," making use of REST protocols, XML file formats, and support for "all languages."

The reference to programming languages drew questions from the audience. What about Java? "You can run it," answered Khalidi. Ruby? "Definitely."

"We want to be very interoperable on this platform, with no data lock-in," Khalidi said.

When asked about Amazon, a potential competitor to Microsoft in cloud services, Khalidi could have gone on the attack, but didn't. "We like Amazon," he said, acknowledging, "They're ahead of us."

Neither Vogels nor Khalidi made mention of the Open Cloud Manifesto, which was introduced earlier in the day with the backing of Cisco, EMC, IBM, Sun, and more than two dozen other vendors. In other words, Amazon and Microsoft are pursuing interoperability on their own terms. That may raise the ire of those who favor industry consensus over self-proclaimed interoperability, but either way, they're steps in the right direction.