標準號：SIS SS-ISO 9040-1991
中文標準名稱：信息技術．開放式系統交換．虛擬終端基本類服務
英文標準名稱：Information technology — Open Systems Interconnection — Virtual Terminal Basic Class Service
發布日期：1991/1/30 12:00:00
實施日期：1999/12/31 12:00:00
適用范圍：Thls International Standard defines, In an abstract way, the externally vlslble Basic Class Virtual Terminal Service wlthin the OS I Application Layer In terms ofa) a model definlng the interaction between users of the service;b) the primitive actions and events of the service;c) the parameter data associated wlth each primitive action and event;d) the relatlonshlp between, and the valid sequences of, these actions and events.The service defined In thls International Standard is that which Is provlded by the OSl Basic Class Virtual Terminal Protocol (in conjunction with the Association Control Service Element and the Presentation Service) and which may be used by any user Includlng other Application Service Elements. The rela-tionship between the standards for Virtual Terminal Service, Virtual Terminal Protocol, ACSE, Presentation Layer Service and the user of the Virtual Terminal Service is shown in figure 1.This International Standard also defines two standard default vIrtual terminal environment profiles and descrlbesthe form of registered virtual terminal environment profiles and control objects. Virtual terminal environment profiles define sets of virtual terminal environment parameters for use in the estab-lishment of virtual terminal associations and subsequent nego-tiation. Thls International Standard also defines a structure ofVT-userVirtual Terminal ProtocolACSEPresentation ProtocolVirtual Terminal Service provides servicebased on service provided — by ACSE serviceand Presentation ServiceFigure 1 - Relatlonshlp of thls International Standard to other OSl Application Layer StandardsASN.1 Object Identifiera for theobjectsdefined inthis International Standard and for use in a register of vlrtual terminal objects.This International Standard does not specify individual im-plementatlons or products, nor does it constrain the im plemen-tation of entities and interfaces within a computer system. There is, therefore, no requirement for conformance to this International Standard.This International Standard applies to Interactive applications requiring terminal oriented communication expressed in terms of the transmission and manipulation of graphical images having the following characterlstics:e) the images are composed of character-box graphic elements organised into a one, two or three dimensional struc-ture;f) attributes may be assoclated with any graphic element to qualify its mode of display.Control information for the communication can be modelled using virtual terminal control objects, and multiple devices can be modelled using virtual terminal devlce objects linked to the other virtual terminal objects.