Is PaaS Just Outsourced Application Server Platforms?
There’s a growing focus on PaaS (Platform as a Service), particularly as Microsoft has been rolling out Azure and VMware continues to push forward with its SpringSource acquisition. Amazon, though generally labeled as IaaS (Infrastructure as a Service) is also a “player” with its SimpleDB and SQS (Simple Queue Service) and more recently, its SNS (Simple Notification Service). But there’s also Force.com, the SaaS (Software as a Service) giant Salesforce.com’s incarnation of a “platform” as well as Google’s App Engine. As is the case with “cloud” in general, the definition of PaaS is varied and depends entirely on to whom you’re speaking at the moment. What’s interesting about SpringSource and Azure and many other PaaS offerings is that as far as the customer is concerned they’re very much like an application server platform. The biggest difference being, of course, that the customer need not concern themselves with the underlying management and scalability. The application however, is still the customer’s problem. That’s not that dissimilar from what enterprise-class organizations build out in their own data centers using traditional application server platforms like .NET and JavaEE. The application server platform is, well, a platform, in which multiple applications are deployed in their own cozy little isolated containers. You might even recall that JavaEE containers are called, yeah, “virtual machines.” And even though Force.com and Google App Engine are proprietary platforms (and generally unavailable for deployment elsewhere) they still bear many of the characteristic marks of an application server platform.How AJAX can make a more agile enterprise
In general, we talk a lot about the benefits of SOA in terms of agility, aligning IT with the business, and risk mitigation. Then we talk about WOA (web oriented architecture) separately from SOA (service oriented architecture) but go on to discuss how the two architectures can be blended to create a giant application architecture milkshake that not only tastes good, but looks good. AJAX (Asynchronous JavaScript and XML) gets lumped under the umbrella of "Web 2.0" technologies. It's neither WOA nor SOA, being capable of participating in both architectural models easily. Some might argue that AJAX, being bound to the browser and therefore the web, is WOA. But WOA and SOA are both architectural models, and AJAX can participate in both - it is neither one or the other. It's seen as a tool; a means to an end, rather than as an enabling facet of either architectural model. It's seen as a mechanism for building interactive and more responsive user interfaces, as a cool tool to implement interesting tricks in the browser, and as yet another cross-browser incompatible scripting technology that makes developer's lives miserable. But AJAX, when used to build enterprise applications, can actually enable and encourage a more agile application environment. When AJAX is applied to user-interface elements to manipulate corporate data the applications or scripts on the server-side that interact with the GUI are often distilled into discrete blocks of functionality that can be reused in other applications and scripts in which that particular functionality is required. And thus services are born. Services that are themselves agile and thus enable broader agility within the application architecture. They aren't SOA services, at least that's what purists would say, but they are services, empowered with the same characteristics of their SOA-based cousins: reusable and granular. The problem is that AJAX is still seen as an allen wrench in an architecture that requires screwdrivers. It's often viewed only in terms of building a user interface, and the services it creates or takes advantage of on the back-end as being unequal to those specifically architected for inclusion in the enterprise SOA. Because AJAX drives the development of discrete services on the server-side, it can be a valued assistant in decomposing applications into its composite services. It can force you to think about the services and the operations required because AJAX necessarily interacts with granular functions of a service in a singular fashion. If we force AJAX development to focus on the user-interface, we lose some of the benefits we can derive from the design and development process by ignoring how well AJAX fits into the service-oriented paradigm. We lose the time and effort that goes into defining the discrete services that will be used by an AJAX-enabled component in the user-interface, and the possibility of reusing those services in the broader SOA. An SOA necessarily compels us to ignore platform and language and concentrate on the service. Services deployed on a web server utilizing PHP or ASP or Ruby as their implementation language are no different than those deployed on heavy application servers using JSP or Java or .NET. They can and should be included in the architectural design process to ensure they can be reused when possible. AJAX forces you to think in a service-oriented way. The services required by an AJAX-enabled user-interface should be consistent with the enterprise's architectural model and incorporated into that architecture whenever possible in order to derive agility and reuse from those services. AJAX is inherently an agile technology. Recognizing that early and incorporating the services required by AJAX-enabled components can help build a more agile, more consistent, more SOA-like application infrastructure.
