There was legitimate debate at one point whether the style of cloud computing often called Platform-as-a-Service (PaaS) was really going to take off in a big way.
The aim of PaaS is to supply developers with a set of services that they can use to build scalable applications without doing all the underlying grunt work themselves.
Such a platform might automatically add additional capacity in response to increased load. Or it could offer various middleware services, such as databases and application servers. (The National Institute of Standards and Technology has a definition document that I and many others use to help make sure we're all on the same page when it comes to the types and characteristics of cloud computing.)
As is always the case with such things, the lines between what is a platform and what is just infrastructure and what is end-user hosted software blur a bit. But, in the main, platforms are a higher level of abstraction than infrastructure but don't offer something that's directly useful for end-users out of the box.
The questions about PaaS were at least two-fold.
For one thing, while cloud infrastructure has a fairly clean correspondence to physical and virtual infrastructure in a data center and Software-as-a-Service is just hosted software in many respects, PaaS doesn't map especially well to familiar concepts. It's partially related to middleware but also includes forms of background automation that haven't historically existed.
There's also the lock-in concern. Cloud infrastructure services like Amazon EC2 and S3 aren't standardized in a formal way. But their interfaces are straightforward enough that a third-party like RightScale can map them across different providers. Alternatively, others can treat them as effectively a de facto standard and mimic them for their own implementations as Eucalyptus is doing.
But PaaS is more vendor specific and the more layers of specialized function, the more specific it becomes. But this doesn't concern everyone. For example,told me that he generally endorsed the idea of vendors competing on the basis of unique differentiation that users need. As he put it: "I don't see benefit to getting the exact thing from three different providers; then you're just competing on price, not features." And the reality is that moving from one vendor's middleware and other supporting application infrastructure to another's has never been an easy and transparent process.
However, upon reading aby fellow CNET Blog Network writer James Urquhart, it's becoming clear to me that PaaS is an important component of cloud computing.
Microsoft'sat its Professional Developer Conference was, by all appearances, a big hit. I've personally viewed Azure as a major bellwether for PaaS, given the large Microsoft development community. If Azure clicks with .Net developers, it bodes well for the PaaS concept.
James also notes that "Ruby on Rails platform service vendor Heroku reportedly hosts more than 40,000 applications now. At its Dreamforce conference in San Francisco, Salesforce.com mentioned it had approximately 135,000 applications running on its Force.com platform" and that "anecdotal evidence suggests there is a large body of Web application developers running on both the Java and Python instances" of Google App Engine.
Google App Engine's relatively low profile was one reason to be somewhat skeptical of PaaS a year ago. Today, I'm still unconvinced App Engine is living up to some of the early expectations that surrounded it. Nonetheless, in the context of clear PaaS advances elsewhere, it's another data point for an at least moderately popular offering.
To these, I'd add that cloud infrastructure is expanding and morphing into something that looks more like a platform. Newer Amazon services such as Elastic MapReduce and Relational Database Service blur the line between what is infrastructure and what is something more. Arguably, Simple Queue Service already did this from the early days but the new services can increasingly handle the mechanics of scaling an application transparently to a developer.
In fact, given such this apparent demand for more abstraction and higher-level services, I wonder if we're starting to see cloud infrastructure essentially morph into a platform.