ThedevelopmentoftheSemanticWebproceedsinsteps,eachstepbuildingalayerontopofanother.Thepragmaticjustificationforthisapproachisthatitiseasiertoachieve()onsmallsteps,whereasitismuchhardertogeteveryoneonboardiftoomuchisattempted.Usuallythereareseveralresearchgroupsmovingindifferentdirections;this()ofideasisamajordrivingforceforscientificprogress.However,fromanengineeringperspectivethereisaneedtostandardize.So,ifmostresearchersagreeoncertainsuesanddisagreeonothers,itmakessensetofixthepointsofagreement.Thisway,evenifhemoreambitiousresearcheffortsshouldfail,therewillbeatleast()positiveoutcomes.Oncea()hasbeenestablished,manymoregroupsandcompanieswilladoptit,insteadofwaitingtoseewhichofthealternativeresearchlineswillbesuccessfulintheendhenatureofthesemanticwebissuchthatcompaniesandsingleusersmustbuildtools,addcontent,andusethatcontent.Wecannotwaituntilthefullsemanticwebvisionmaterializes-itmaytakeanothertenyearsforittoberealizedtoitsfull(请作答此空)(asenvisionedtoday,ofcourse).
A.area
B.goal
C.object
D.extent
正确答案是D