i think that a Web Service can be seen as an object, that communicates with other web service objects via Network, such as the Internet.
these web service objects can depend on interfaces instead of implementation, and use remote objects as implementations.
an object registry can be used to query & locate web service implementation we want to use in the Internet, and to establish connection with such.
known standard for such registry is UDDI, for communication with remote objects it's SOAP.
that way we can construct a running program, a process, a graph of collaborating objects from partial solutions in the Internet.
See also: SOA and Web Services.