We can think of the Cloud Access Layer as a "bus", and here we could start thinking about ESB (Enterprise Service Bus), but it is not the case. The ESB is something that works at a higher level of abstraction, ESB runs at business application level.

What is needed to move up and down services from/to the cloud is a standard common interface, based on the use of standards that should include:

1. Grant independence to cloud based applications, so they don’t need to be aware of its own cloud services (which are used to run the business).

2. Change providers without a trauma, i.e., have a common standard API.

3. Go up and down from the cloud as needed.



1. Independence.

It is a basic criterion for application design. In fact, it is not a new paradigm the fact that applications should be developed in response to that independence from the infrastructure on which they run.

40 years ago the concept of operating system to isolate applications from the management of the processor, memory or disk space was coined. More recently, about 20 years ago, the driver concept appeared to isolate the treatment of different devices from the application’s point of view (think for example in the management of printers).

More recently Application Servers arisen to isolate developers from having to deal with problems such as connecting to a database, use a messaging subsystem, or the actual interface with users (typically web browsers).

Well, according to this evolution, applications that use cloud resources should be independent of the cloud resources they access, and that independence must easily allow activities such a change of provider.