[WG-UMA] An interesting scenario for UMA

[Alan Karp]

Bob offers a Backup service that takes a reference to a service that
will provide the data to be backed up.  Bob's service is implemented
by invoking Carol's copy service, which takes a reference to a service
that provides the data to be copied and a reference to a service that
will hold the copy.  Alice invokes Bob's service providing a reference
to a service that will provide the data she wants backed up.

This very simple example has many features of real web services
composition. Services invoke other services, and services take
references to other services as parameters. Further, it may not be
possible to change the service implementation. For example, we might
want to change Carol’s service to take the bits representing the files
instead of references to services that provide them, but we must be
prepared to deal with legacy applications.

Section 2 of

http://www.hpl.hp.com/techreports/2008/HPL-2008-204R1.pdf (Best Paper,
ARES 2010)

describes this scenario in more detail.  In that paper, we look at the
consequences of various choices Alice makes for the input service and
Bob’s service makes for output service.

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Alan Karp