What's the first thing you should do if you're thinking of developing software for cloud computing? At ZendCon, Zend Technologies user group yesterday, three members of a five member panel answered the same way: adopt Simple Cloud API, the open source cloud services interface.Simple API for Cloud Application Services was announced Sept. 22 as an open source project for cross cloud operations. If you adopt Simple API, your application will be able to call the same service from different clouds. If you need storage in the cloud, build the Simple API for storage services into your application and you will be able to use storage in either Amazon EC2 or Nirvanix Storage Delivery Network. Amazon doesn't provide support for Simple API the way Nirvanix does, but the Eucalyptus open source code project has generated an open source version of its S3 storage API that can stand in.

The panel Tuesday was called Developing On the Cloud, and Wil Sinclair, Zend's cloud strategist, said the tooling you use to build cloud software -- the applications you need to interoperate with cloud services -- will have a big impact on what you can do. If you start out by using a proprietary cloud's tools and develop software to work with it, your investment will tend to work only with that cloud and will have limited value. If you adopt the Simple API for Cloud Application Services, it will work with all clouds that support it, he told a crowd of about 150 PHP developers yesterday at the San Jose Conference Center. Sinclair leads the Zend effort to win adherents to Simple API so his views are predictable. The same can be said, I guess, for two other panel members, IBM's Doug Tidwell and Microsoft's Vijay Rajagopalan, whose firms both endorse Simple API. Zend, as the maker of PHP scripting language and tools, is the host of the Simple API project. PHP is frequently used in Web applications. It's likely to be frequently used in cloud applications.

IBM and Microsoft might prefer to set standards that others follow, but in this case they are in favor of following standards. They're behind the leaders in cloud computing. Standards open the door to playing catch-up. Amazon.com, VMware and more specialized outfits, such as Engine Yard and Rackspace, have a jump on other vendors.

Microsoft is about to launch its Azure cloud at its Professional Developer's Conference in Los Angeles Nov. 16.

Andi Gutmans, CEO of Zend, said during a keynote at the conference that Microsoft is interested in getting as many developers as possible to use Azure. Microsoft isn't just interested in Visual Studio and .Net developers. It wants Eclipse-based tools and the developers who use them to work in Azure as well. One way it can do so is to provide an API to Eclipse that let's PHP programmers inside Eclipse reach services in Azure and it is likely to do so.

Microsoft's interest in and cooperation with open source PHP is well known. For other languages, there's still a question mark. We'll know that Simple API is opening things up for sure if we see Microsoft provide Eclipse with an API for Java tool users that enables them to work with Azure as well.