"With the resurgence of SaaS or at least the next stage in evolution of it, some are confused about the direction and or the definition of said stage. Some call it next-gen platform, SaaS 2.0, On-Demand, Integration as a Service (IaaS) . The market will decide upon a name. But what will this name represent? Just as SaaS used to be called ASP, I think IaaS or SaaS 2.0 could be best explained by revisiting what composite applications are all about. That is really what everyone is talking about. The integration of atomic web services through a (hopefully agnostic) platform that doesn't sit on the server or client, but is not middleware. This is the future of Enterprise applications or Enterprise 2.0. This is the driving power of the concept of web 2.0. Finally utilyzing the services that can be exposed through SOA." Mike Wagner
"Composite applications" may be a new term for some, although the concept was first named by Gartner in December 1997. Old idea or new, the principles of composite applications are important to most enterprise software projects and to most business software vendors. A poorly designed composite application can endanger the performance and integrity of established production applications. A well-designed composite application can help enterprises reduce costs of IT services and improve time to market for new IT initiatives. For most enterprises, the composite-application style is not a choice to ponder, but a reality to make the best of. Gartner research in this Spotlight is a must-read for most engineers, designers and architects involved in the planning and development of business applications.
A composite application is an application (typically, an interactive user-facing application) that draws on resources of other applications to complete its work. Such an application looks to the user like a regular new interactive application, yet in reality it may be only 10 percent new and 90 percent an assembly of pre-existing (purchased or in-house "legacy") components or data. The "glue" that brings a composite application together is always integration technology. Composite applications are a style of application integration. Composite application projects, along with other integration projects, should be managed with the participation of the integration competency center.
Well-designed composite applications are heavy users of service-oriented architecture (SOA). This affinity draws composite applications into the current industry hype. Many promises and vendor demonstrations are given for SOA, using assemblies of homogeneous Web services. Although these simple assemblies are easy to demonstrate, they are not composite applications. Only assemblies that engage multiple applications and thus require integration of distinct data models are composite applications. Simple homogeneous assembled applications do not deliver most of the benefits of integrated composite applications, nor do they carry their risks. Beyond the hype, the real composite applications require careful design and planning. The effort is often worth it because benefits of composite applications can be great — but rumors of the simplistic "point and click" production of composite applications are highly exaggerated.
I forsee a convergence of AJAX and SOA players that meet somewhere in the middle but are not middleware. Exiting times are upon us.