1. A method executed by a processor of instantiating a template in a composite application infrastructure, said method comprising: in a template library accessible to a computer system, storing a template describing a composite application having a plurality of application components, wherein said template defines interactions between the plurality of application components and includes a composite application component assembly descriptor listing each of said plurality of application components of said composite application; instantiating said composite application using said template by: registering, in an application instance registry of the computer system, a plurality of composite application instances of the composite application and respective instance information specifying respective parameters for each of the plurality of composite application instances, wherein each of said plurality of composite application instances is transiently represented in said application instance registry by a respective table entry without creating in data storage of the computer system a real object representing the corresponding composite application instance; in response to initiation of a composite application usage session, dynamically creating in the data storage of the computer system a meta application as a persistent real object in the data storage of the computer system by transformation of a most recent version of the template; during the composite application usage session, creating, as needed, each of multiple composite application instances among the plurality of composite application instances as transient real objects in the data storage by cloning the persistent meta application; and removing the transient real objects corresponding to the multiple composite application instances from the data storage of the computer system after an end of said composite application usage session.