BS ISO/IEC ISP 11185-13:1995 Information technology. International standardized profiles FVT2nn. Virtual terminal basic class. Register of control object type definitions - Part 13. FVT2111. Waiting time control object
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1.1 General
The concept of Profiles for OSI, and the structure of the International Standardized Profiles that document them, are defined in lSO/IEC TR 10000-1. Such Profiles are divided into a number of different classes and sub-classes. Two of these classes contain sub-classes comprising functions of the Virtual Terminal Basic Class Service and Protocol specified in the base Standards ISO 9040 and ISO 9041. These are the Application Profiles (A-Profiles) and the Interchange Format and Representation Profiles (F-Profiles).
The relationship between A-Profiles and F-Profiles is described in 7.3.2 of lSO/lEC TR 10000-1 and is as follows. Application Layer base Standards require, implicitly or explicitly, the structure of information carried or referenced by them to be specified for each instance of communication. lt is the purpose of F-Profiles to specify such information structures. Particular functional requirements may then be met by the combination of an A-Profile with one or more FProfiles.
Establishment of a VT-association involves the selection by negotiation of a particular Virtual Terminal Environment Profile (VTE-profile), and of particular values for any arguments of that VTE-Profile. The VTE-Profile specification, and possibly also the values of certain VTE-Profile arguments, may in turn reference the definitions of VT control Object types and assignment types. These VTE-profiles, control Object types and assignment types are thus information structures that require explicit reference within the VT protocol. Particular instances of these structures are fully defined within the base Standards, but the base Standards also provide for further instances to be defined by registration. Esch registered instance constitutes an F-Profile within the framework of lSO/lEC TR 10000.
The Virtual Terminal Basic Class Service and Protocol may be used to realise a wide range of distinct functions. Particular functions may be realised through the selection of appropriate VT functional units, F-Profiles and other VTEProfile argument values. The specification of the selection required to realise a particular function and to promote interoperability constitutes a Virtual Terminal A-Profile within the framework of lSO/IEC TR 10000.
The three International Registers of VT information structures and the specifications of VT Application Profiles are each published as a separate multi-part ISP as follows:
- lSO/lEC ISP 11184 is the Register of VTE-profiles;
- ISO/IEC ISP 11185 is the Register of control Object type definitions;
- lSO/IEC ISP 11186 is the Register of assignment-type definitions;
- ISO/IEC ISP 11187 contains the specifications of VT Application Profiles.
This part of lSO/lEC ISP 11185 contains the definition of a control Object type that may be used to set a time limit associated with data entry into the display Object during S-mode Operation of a VT-association. The significance of the expiry of this time limit does not form part of this definition and should be specified by any VTE-Profile that references a control Object of this type.
1.2 Position within the taxonomy
The taxonomy of International Standardized Profiles for OSI is laid down in lSO/lEC TR 10000-2. Within the classification scheme of this taxonomy, the OSI Profiles specified in this International Standardized Profile are in the Virtual Terminal Registered Object sub-class of the class of Interchange Format and Representation Profiles.
A Profile within this subclass has a Profile identifier of the form FVTabc, where abc is a structured numerical identifier that identifies the Position of the Profile within each of the three levels of subdivision of the subclass. The values of a and b are Single digits but c is an integer that is not necessarily a Single digit.
In principle the ISO Virtual Terminal model allows for multiple classes of Operation, although at the time of publication of this International Standardized Profile only the Basic Class has been defined. The value of the identifier component a distinguishes between distinct types of information Object as follows:
- a= 1 for Basic Class VTE-profiles;
- a = 2 for Basic Class Control Objects
-a = 2 for Basic Class Control Objects;
-a = 3 for Basic Class Assignment Types.
Values of a developme Ints. greater than 3 are reserved for future This International Standardized Profile lSO/IEC ISP 11185 contains the specifications of the Profiles with identifiers of the form FVT26c. For this form of identifier, the component b distinguishes between the five major classifications of Basic Class Control Objects as follows:
- bz 1 for Miscellaneous Control Objects;
- b = 2 for Field Entry Instruction Control Objects;
- b = 3 for Field Entry Pilot Control Objects;
- b = 4 for Reference Information Objects;
- b = 5 for Termination Conditions Control Objects.
Each of these classifications corresponds to a sub-register under the procedures of ISO/IEC 9834-5. The identifier component c is the serial number of the control Object type in the appropriate sub-register. Values of b greater than 5 are reserved for new classifications of Basic Class Control Objects that may be defined in future amendments to ISO 9040.
This part of ISO/IEC ISP 11185 contains the definition of the Miscellaneous Control Object type with the Profile identifier
FVl-2111 - Waiting Time Control Object.
1.3 Scenario
The specification of the Virtual Terminal Service is given in ISO 9040. lt is based on a model in which two VT-users communicate by means of a shared Conceptual Communication Area (CCA) that is a conceptual part of the VT service-provider. Information exchange is modelled by one VT-user updating the content of the CCA and the changed state of the CCA then being made accessible to the peer VT-User
Control objects (COS) form one of the types of information Object that may be present in the CCA. This is illustrated in figure 1, in which CO-l, CO-2, . . . CO-n represent a number of different control objects present in the CCA. The negotiation during establishment of a VT-association will determine whether or not these will include a control object of the type whose specification is given in this part of ISO/IEC ISP 11185.
The CCA is structured by the Virtual Terminal Service into a number of components. For a control Object the Data Structure Definition (DSD) component of the CCA contains the Syntax of its information content, including the range of possible values and the permitted update operations. The current value of its information content is contained in the Control, Signal and Status store (CSS) component. Updates to the current value take place through the issue of VT Service primitives by one VT-user to the service-provider. Changes of state of the CCA are made accessible through the issue of VT Service primitives by the service-provider to the peer VT-User.
By clause 14 of ISO 9040, COS enable VT-users to handle control information related to virtual terminal functions and to real devices. This control is exercised by the VT-users through semantics associated with the information content and with the update operations of the CO. Definition of the semantics, or specification of the Source of the semantics if the semantic details are not fully prescribed, forms part of the registered definition of the CO. These semantics are not however of concern to the VT service-provider itself. The DSD will contain an ASN.l Object identifier that identifies the registered definition, but the VT service-provider merely acts as a repository of this value. lt is only the VT-user that requires knowledge of the registered definition.
NOTE 1 - The VTE-Parameter values that determine the Syntax of the information content may not be negotiated explicitly during association establishment. Moreover, in the case of non-parametric COS these values do not determine the details of the Syntax. Such values and details form part of the registered definition of the CO. Since the VT service-provider is not required to have knowledge of this registered definition, in principle the VT-users provide the VT service-provider with such information through local management procedures. Whether or not this is necessary in practice depends on the configuration of the implernentations concerned.
Communication procedures; Computer-computer communications; Information exchange; Data transmission; Data transmission control procedures; Open systems interconnection
BS ISO/IEC ISP 11185-13:1995 Information technology. International standardized profiles FVT2nn. Virtual terminal basic class. Register of control object type definitions - Part 13. FVT2111. Waiting time control object
