From MIKE2 Methodology
Composite Applications are next-generation capabilities formulated from services available via the common services layer. A Composite Application usually does not have persistent data of its own. The application uses information from other application data stores or enterprise platforms. A Composite Application is formulated from services available via the common services layer and is likely to contain its own workflow, which uses a repository of transient information. Composite Applications “pull together” existing assets to deliver a larger, more significant capability and may contain capabilities at the integration layer, from an OLTP Application and from another system across the web.
A Composite Application usually does not have persistent data of its own – it uses information from other application data stores or enterprise platforms. Examples of composite applications are listed below.
Composite Business Services
Composite Business Services are capabilities built from multiple loosely coupled Business Services that work together as an "application" to provide a greater degree of functionality.
Mashup
A Mashup is a dynamic application that consolidates two or more services to make them do, in aggregate, what they do not do on their own.
Widgets
A widget is a service with a visual component that makes use of information from another source. Enterprise mashup makers produce a repository of services and widgets.