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we are often asked by people who are trying to understand the value grid technology brings to web services, "what is the significance of grid services? they look like web services." the answer to this question is superficially straightforward: mechanically, the differences between grid services (as defined in the open grid services infrastructure [ogsi] v.1.0 specification) and web services are few: a grid service is simply a web service that conforms to a particular set of conventions. for example, grid services are defined in terms of standard wsdl (web services definition language) with minor extensions, and exploit standard web service binding technologies such as soap (simple object access protocol) and ws-security (web services security). so yes, grid services do look like web services.
what is the significance of grid services? well, these grid service conventions are not superficial in their function; they address fundamental issues in distributed computing relating to how to name, create, discover, monitor, and manage the lifetime of stateful services. more specifically, these conventions support:
named service instances and a two-level naming scheme that facilitates traditional distributed system transparencies (see sidebar) a base set of service capabilities, including rich discovery (reflection) facilities explicitly stateful services with lifetime management
before proceeding further, lets state that clearly its possible, using standard web services, to manage and name stateful services using ad hoc methods, e.g. extra characters placed in urls or extra arguments to functions. similarly, you can define an introspection service interface and publish it via wsdl. however, the point is not whether it can be done, but whether it is ... 下一页