单选题 We initially described SOA without mentioning Web s ervices, and vice versA. This is because they are ortho gonal: service-orientation is an architectural (    ) whil e Web services are an implementation (     ).The two can be used together, and they frequently are, but they are not mutually dependent.For example, although it is widely considered to be a distributed-computing solution,SOA can be applied to advantage in a single system,where services might be individual processes with well-defined (     ) that communicate using local channels,or in a self-contained cluster, where they might communicate across a high -speed interconnect.Similarly, while Web services are(     ) as the basis for a service-oriented environment, there is nothing in their definition that requires them to embody the SOA p rinciples. While(回答此处 )is often held up as a key characte ristic of Web services,there is no technical reason that they should be stateless-that would be a design choi ce of the developerwhich may be dictated by the arc hitectural style of the environment in which the servic e is intended to participate.