GFac adopts a novel approach to create application services on-demand from workflows. When it receives a request from a client to create an application service instance on some host, it instantiates a generic service binary that is pre-installed on that host. GFac then provides the generic service instance with a configuration document that "describes" the application service. We call this configuration document the ServiceMap document. The ServiceMap document is not a WSDL. It is a higher level language than WSDL for describing the "WSDL portType", the security policies and soft-state lifetime management policies of an application service. It is written by the application service provider (also known as service provider or application provider in this context) and registered with a well known Registry service so that it can be retrieved by GFac for creating an instance of that application service. Using the ServiceMap document, the generic service instance configures itself to "become" the application service instance. The application service instance then generates its WSDL and registers it with a Registry service. GFac then returns the application service's WSDL in the response message to the client. The client can then use the application service's WSDL to invoke it directly.
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