NTIN36@gec-b.rutherford.ac.uk (Jim Craigie) (11/05/90)
Steve,
I append the clause defining General Text from ISO/IEC 10021-7 because
it changed substantially at DIS ballot resolution and ISO haven't quite
published 10021 yet. It allows carrige of character repertoires defined
in other standards including (amongst others) 6937, 8859 and 10646.
Jim
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[|B.2 General Text
A General Text extended body part represents character text
of a general nature. It has Parameters and Data components.
general-text-body-part EXTENDED-BODY-PART-TYPE
PARAMETERS GeneralTextParameters IDENTIFIED BY id-ep-general-text
DATA GeneralTextData
::= id-et-general-text
GeneralTextParameters ::= SET {
g0-designator [0] CharacterSetDesignator OPTIONAL,
g1-designator [1] CharacterSetDesignator OPTIONAL,
g2-designator [2] CharacterSetDesignator OPTIONAL,
g3-designator [3] CharacterSetDesignator OPTIONAL,
c0-designator [4] CharacterSetDesignator OPTIONAL,
c1-designator [5] CharacterSetDesignator OPTIONAL}
GeneralTextData ::= GeneralString
The Parameters component comprises the designators of the G0, G1, G2,
G3, C0 and C1 sets that may be present in the Data component. Each
character set designator is represented by the escape sequence defined
in the registration of that character set, registered in accordance
with ISO 2375.
The absence of the G0 and C0 designators imply the use of the
characters sets registered with registration numbers 2 and 1
respectively. The absence of the other designators imply that the
corresponding set is not designated.
CharacterSetDesignator ::= GeneralString (SIZE(3..5))
The Data component comprises a single General String. G and C sets
other than those defined in the Parameters component shall not be
used.
Each General String shall be encoded using 8-bit encoding (not 7-bit).
Within the Data component, lines may be of any length. Whenever the
component is rendered (e.g., displayed to or printed for a user), all
(rather than only a part) of the text must be communicated (e.g.,
lines may be folded but shall not be truncated).
For this extended body part type, externally defined EITs are defined
(pursuant to item c of clause 20.4) as follows. One EIT is defined for
each G or C set the Parameters component has identified either
implicitly or explicitly. It is denoted by the Object Identifier
assigned to that character set.
This annex acts as the registration authority for such Object
Identifiers, as follows. All the Object Identifiers are allocated as
leaves immediately under the single vertex representing this
registration authority (id-cs-eit-authority). The Object Identifier
component identifying the character set represented by the leaf is the
registration number of that character set as allocated in accordance
with ISO 2375.
EXAMPLE - The externally defined EITs for Latin Alphabet number 1
(ISO 8859-1) are {id-cs-eit-authority 6} for the G0 set and
{id-cs-eit-authority 100} for the G1 set.
NOTES
1. The defaults for the G0 and C0 character set designators are those
assumed as designated and invoked by the ASN.1 Basic Encoding Rules
(ISO 8825) for a General String.
2. These Basic Encoding Rules require that the escape sequences for
the G1, G2, G3 and C1 character set designators are repeated within
the encoding of the General String. The G sets then have to be invoked
using locking shift or single shift control functions.]