Questions about concept of Web service

Dear Sir:
I am a teacher from Lanzhou University, P.R China. I am very interesting in Web
services. When I meet the defination of Web service, I have two questions: (1)What
does Web service mean, a specification, an architecture, a solution,or other?
(2)May the techniques, such as URI,XML and internet ,which implement Web services,
be ommited from the concept of Web service ? As we know, a model may be
independent of its implementing techniques.
Excepting your responses, Thanks!

                 yours xuyusheng