A basic premise of OGSA is that everything is (66) by a service: a network enabledentity that (67) some capability through the exchange of messages. Computational resources, storage resources, networks, programs, databases, and so forth are all (68) . This adoption of auniform service-oriented model means that all components of the environment are virtual. Morespecifically, OGSA represents everything as a Grid service: a Web service that conforms (69) a set of conventions and supports standard interfaces for such purposes as lifetime management. This core set of consistent interfaces, from which all Grid services are implemented. (70) the construction of hierarchical, higher - order services that can be treated in a uniform way across layers of abstraction.
70（）
A．forms
B．groups
C．consist
D．Facilitates