Mashups
"Mashups" is a term typically used to describe the integration of services at the web page UI level to create rich web applications with lots of functionality behind them delivered by several different web sites. For example, you could create a web page that has maps, news, weather, and other information all drawn from different remote web application services and integrated with a custom layout look-and-feel. In this case, the SaaS is delivered at the point of the UI. This goes against the grain of an SOA in that it locates logic in the UI to access services where it is only useful to the UI client and cannot be reused by other types of clients.
For example, consider a case where you have nonUI clients such as business systems that want to make use of geocoding services to lookup latitude/longitude coordinates for a given address. If you put your logic to access remote geocoding services in a web page UI, this is not accessible to your nonvisual business-system client components. However, if you provide your geocoding access through a Mapping Service accessible as a web service using SOAP/HTTP, then you support its use for all your clients, both UI and nonUI.
In my SOA example, the Address Service depends on the Mapping Service. This is an illustration of the important concept in SOA that services can depend on each other, and new higher level, more abstract services can build on and reuse or delegate to lower level, more foundational services. This concept is important in the convergence of SOA and SaaS because it illustrates how local SOAs will merge to form federated SOAs and new higher level, more abstract services may be developed that depend on other lower level foundation services that already exist.
In summary, to best leverage SOA and SaaS, you want to do your mashing up or accessing SaaS from behind services, and not in UIs. This approach does not prevent all the benefits of new rich web UIs that leverage powerful mashup tools such as AJAX. It simply means that your AJAX-enabled web UIs talk to your local service interfaces, which may in turn talk to remote services, and your web pages can focus on presentation rather than connecting to remote services.
