Attributes to services
Services are made avaliable through a ServiceEntry.
This entry contains a proxy, implementing a service-interface and thus hiding
and adstracting from the actual way the fucntionality of that interface is
implemented.
It also contains a world-wide unique identifier (partly randomly generated
and very long to avoid conflicts) and
a set of Attributes.
These attributes can be atached, not only by the servie itsefd but by users
and other services.
They describe the placement of a service (for example a printer-service's
printer), give a description, the version and implementor/vendor of a service
and also the
representations.
Thus it is possible to write and atach a new represnetation for a unique
user-interface, that uses the service-interface and atach it to any service
implementing that interface without knowing about the iner working of it,
not even what computer it runs on.