Here’s a simple breakdown of the four stages in cloud provision.
Infrastructure as a Service (IaaS) – At this stage basic virtual machines, virtualised storage and network access are made available to users. Those users are responsible for providing and loading their own operating systems, management systems, middleware and applications. Commercial examples include S3 from Amazon, BlueCloud from IBM, and Project Caroline from Sun.
Platform as a Service (PaaS) – This adds to IaaS a pre-configured operating system and middleware. The user remains responsible for providing and managing their own applications. Commercial examples include EC2 from Amazon, App Engine from Google, Windows Live from Microsoft, Force.com from Salesforce.com and SuiteFlex from NetSuite.
Software as a Service (SaaS) – This builds on IaaS by transferring responsibility for the application software to the cloud service provider. Commercial examples include Office Live from Microsoft, Zimbra from Yahoo Salesforce.com and Google Apps.
Business Process as a Service (BPaaS) – At this final point the cloud service provider would provide a complete suite of applications to perform a major business function or functions, including taking responsibility for integration between those applications. Commercial examples include Infosys BPaaS and IBM SmartCloud.
The four stages are also well described in the Institution of Engineering and Technology’s Factfile, Cloud computing.
For more on cloud computing and open source software be sure to check out our recently released report – Open for business and the accompanying animation as well as an infographic detailing Amadeus in the cloud.