1. A system for generating an On-Demand reconfigurable Web application that provides create/read/update/delete-functionality on data managed in one or more external data sources, the system comprising a general stand-alone software application with code for: a) providing an abstraction layer to the external data sources and to one or more computation services, b) accessing an XML-based definition of desired create/read/update/delete-functionality in pre-defined form, c) graphical interfaces on functionality, d) non-typed definitions of data in the data sources, data logic related to the data sources and the various relationships between these items; and e) parsing, upon receipt of a request to have the Web application perform an action, the XML-based definition, presenting one or more of the defined graphical interfaces and/or executing the functionality from the XML-based definition that is associated with the action, using the abstraction layer to obtain access to the data managed in the external data sources and applying On-Demand-Instantiation to type the non-typed objects within the context of the definition of the functionality being executed.