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-l. 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-l 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 such information 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 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 attribute assignment types. These VTE-profiles, control object types and attribute assignment 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 fun ctions 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 attribute assignment type definitions; - ISO/IEC ISP 11187 contains the specifications of VT Appli cation Profiles.

This part of ISO/IEC ISP 11186 contains the definition of a font assignment type that enables a font assignment value to be specified as a font resource property-list in accordance with ISO/IEC 9541-1. The properties that may be included in the property-list are specified as a subset of the properties defined for a character cell font. Particular provision is made for font resources in which the height and width of a character cell are integer multiples of the height and width of the character boxes that comprise the graphical images considered by the VT service. Provision is also made for the use of both left- to-right and right-to-left writing modes and for the coexistence of both modes in the display object.