1

Scope

1.1 General The concept of Profiles for OSI, and the structure of the International Standardized Profiles that document them, are defined in ISO/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 ISO/IEC 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. It is the purpose of F-Profiles to specify Information Objects that provide these structures. Particular functional requirements may then be met by the combination of an A-Profile with one or more F-Profiles.

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 VT E-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 assignmen t types are therefore Information Objects that require explicit reference within the VT protocol. Particular instances of these Information Objects are fully defined within the base standards, but the base standards also provide for further instances to be defined by registration. Each registered instance constitutes an F-Profile within the framework of ISO/IEC 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 VTE- profile 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 ISO/IEC TR 10000.

The three International Registers of VT information objects and the specifications of VT Application Profiles are each published as a separate multi-part ISP as follows:

- ISO/IEC ISP 11184 is the Register of VTE-profiles; - ISO/IEC ISP 11185 is the Register of control object type definitions; - ISO/IEC ISP 11186 is the Register of assignment-type definitions; - ISO/IEC ISP 11187 contains the specifications of VT Application Profiles.

It is a requirement of ISO/IEC 9646-7 that the specification of an Information Object shall provide an Information Object Implementation Conformance Statement (ICS) proforma. This is a document in the form of a questionnaire or checklist to be completed by the supplier or implementor of an implementation for whi ch conformance is claimed to the Information Object concerned. It is also a requirement of ISO/IEC 9646-7 that the specification of a Profile shall provide a Profile Requirements List (Profile RL) which modifies the ICS proformas of the referenced base standards. A Profile specification may in addition provide a Profile Specific ICS proforma.

This part of ISO/IEC ISP 11187 provides guidance on the interpretation of these requirements for Profiles of the Virtual Terminal Basic Class Service and Protocol. It also specifies a Common RL for the VT Protocol that shall be incorporated by reference into each VT Application Profile specified in other parts of ISO/IEC ISP 11187.

1.2

Position within the Taxonomy The taxonomy of International Standardized Profiles for OSI is laid down in ISO/IEC TR 10000-2. Within the classification scheme of this taxonomy, Profiles of the Virtual Terminal Registered Objects subclass of the class of Interchange Format and Representation Profiles (F-Profiles) have taxonomy identifiers of the form FVTabc. Profiles of the Virtual Terminal subclass of the class of Application Profiles requiring connection-mode Transport Service have taxonomy identifiers of the form AVTbc. In these identifiers, abc and bc are structured numerical identifiers in which values of a and b are single di gits but c is an integer that is not necessarily a single digit. These numerical identifiers identify the position of the Profile within the hierarchy of levels of subdivision of the subclass.

The guidance on RLs and ICS proformas given in this part of ISO/IEC ISP 11187 is applicable to all Profiles in either of these two subclasses. The Common RL for the VT Protocol given in this part of ISO/IEC ISP 11187 is applicable to all Application Profiles with identifiers of the form AVT1c or AVT2c. Other parts of this ISP give either further common requirements or the specification of an individual Application Profile with an identifier of one of these forms. The value of the identifier component b in the identifiers AVTbc distinguishes between permitted modes of operation of the Virtual Terminal Service as follows:

- b = 1 for Basic Class A-mode (asynchronous mode); - b = 2 for Basic Class S-mode (synchronous mode).

Values of b greater than 2 are reserved for future developments.