ISO/IEC 9541-1:1991

ISO/IEC
INTERNATIONAL
9541-1
STANDARD
First edition
1991-09-15
Information technology - Font
information interchange -
Part 1:
Architecture
- fkhange d’informations sur /es
Technologies de I’information
fontes -
Partie 1: Architecture
Reference number
ISO/1 EC 9541-1: 1991 (E)
--
P -- Y

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lSO/lEC 9541=1:1991(E)
Contents
Page
1 Scope . 1
2 Normative references . 1
3 Definitions . 2
4 Notation . 3
5 Data types . 4
5.1 General . 4
5.2 Properties and property-lists
.................................................. 4
5.3 Values and value-lists
............................................................. 4
5.4 Structured-names . 5
5.4.1 ISO/IEC 9541 and lSO/IEC 10036 names . 5
5.4.2 ICDOOI 0 names .
6
5.5 Formal notation
....................................................................... 6
6 Glyph identification . 8
6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.2 ISO/IEC 10036 glyph names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.3 ISO/1 EC 10036 glyph registration authority . 8
7 Glyph collection identification .
8
7.1 General
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.2 lSO/IEC 10036 glyph col ection names . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.3 lSO/IEC 10036 glyph col
ection registration authority . . . . . . . . . . . . 9
8 Font resource
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Q
8.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . u
8.1.1 Font resource name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
8.1.2 Font resource description properties
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8.1.3 Font resource modal properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
0 ISO/IEC 1991
All rights reserved. Unless otherwise specified no part of this publication may be reproduced
or utilized in any form or by any means, electronie or mechanical, including photocopying and
microfilm, without Permission in writing from the publisher.
ISO/1 EC Copyright Office l Case Postale 56 l CH-l 211 Geneve 20 l Switzerland
Printed in Switzerland
ii

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ISO/IEC 9541=1:1991(E)
................................................. 10
8.1.3.1 Writing mode properties
8.1.3.2 Glyph metrics properties . 10
............................. 10
8.1.4 Glyph shape representation properties
Formal data type definition of a font resource . 10
8.1.5
82 . Glyph coordinate System . 11
Linear scaling model . 12
8.3
84 . Extensibility . 13
............. 13
85 . Specification of font resource name (FONTNAME)
.
86 Description of font resource description properties
........................................................... 13
(FONTDESCRIPTION)
14
8.6.1 Data Version (DATAVERSION) . .
.......................... 14
8.6.2 Standard Version (STANDARDVERSION)
8.6.3 Data Source (DATASOURCE) . 14
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.6.4 Data Copyright (DATACOPYRIGHT)
8.6.5 Design Source (DSNSOURCE) . . . . . . . . 15
................................. 15
8.6.6 Design Copyright (DSNCOPYRIGHT)
8.6.7 Relative Rational Units (RELUNITS) . 15
8.6.8 Typeface Name (TYPEFACE) . . . . . . . . . . . 16
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8.6.9 Font Family Name (FONTFAMILY)
8.6.10 Posture (POSTURE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8.6.11 Posture Angle (POSTUREANGLE) . 17
8.6.12 Weight (WEIGHT) . . . . . . . . . . . . . . . . . . . . . I B. . 17
...............................
8.6.13 Proportionate Width (PROPWIDTH) 18
8.6.14 Structure (STRUCTURE) . . . . . . . . . . . . . . . . 18
Design Group (DSNGROUP) . . . . . . . . . 19
8.6.15
8.6.16 Glyph Complement (GLYPHCOMP) . 19
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.6.16.1 Number of Glyphs (NUMGLYPHS) 20
8.6.16.2 Included Glyph Collections (INCGLYPHCOLS) . 20
........... 20
8.6.16.3 Excluded Glyph Collections (EXCGLYPHCOLS)
8.6.16.4 Included Glyphs (INCGLYPHS) .
20
8.6.16.5 Excluded Glyphs (EXCGLYPHS) . 21

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ISO/IEC 9541=1:1991(E)
8.6.17 Design Size, Recommended Minimum and Maximum Size
(DSNSIZE, MINSIZE, MAXSIZE) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.6.18 Capital Height (CAPHEIGHT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.6.19 Lowercase Height (LCHEIGHT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.6.20 Minimum Feature Size (MINFEATSZ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
. . 22
8.6.21 Nominal Capital Stern Width (NOMCAPSTEMWIDTH)
8.6.22 Nominal Lowercase Stern Width (NOMLCSTEMWIDTH) 23
8.6.23 Nominal Writing Mode (NOMWRMODE) . . . . . . . . . . . . . . . . . . . . . . 23
8.7 Specification of font resource modal properties (WRMODES) 23
8.7.1 Writing Mode (WRMODE) 24
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.7.1 .l Writing Mode Name (WRMODENAME) . 26
8.7.1.2 Nominal Escapement Direction (NOM ESCDI R) . 26
8.7.1.3 Escapement Class (ESCCLASS) . . 26
8.7.1.4 Average Escapement (AVG ESCX, AVG ESCY) . 27
8.7.1.5
Average Lowercase Escapement (AVG LCESCX,
AVGLCESCY) . 27
8.7.1.6 Average Capital Escapement (AVGCAPESCX,
................................................................ 28
AVGCAPESCY)
8.7.1.7 (TAB ESCX, TAB ESCY) 28
Ta bular Escapement .
28
8.7.1.8 Maximum Font Extents (MAXFONTEXT) .
8.7.1.9 Seetors-Pairwise Escapement Adjustment Descriptions
(SECTORS) . 29
8.7.1.10 Escapement Adjustments (ESCADJS) . . . . . . . . . . . . . . . . . . . . . . . . 29
8.7.1.10.1 Escapement Adjustment (ESCADJ) . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.7.1 .lO.l.l Escapement Adjustment Mode Name
(ESCADJNAME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.7.1.10.1.2 Class-Pairwise Escapement Adjustments (CPEA) . . 30
8.7.1 .10.1.3 Scale Escapement Correction (SEC) . . . . . . . . . . . . . . . . . . . . . . . 32
8.7.1 .ll Recommended Pairwise Escapement Adjustment Size
(MINESCADJSZE, MAXESCADJSZE) . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.7.1.12 Scores (SCORES) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.7.1 A2.1 Score (SCORE)
8.7.1.12.1.1 Score Name (SCORENAME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
8.7.1.12.1.2 Score Position Offset (SCOREOFFSETX,
35
SCOREOFFSETY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iv

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ISO/IEC 9541=1:1991(E)
8.7.1.12.1.3 Score Thickness (SCORETHICK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
8.7.1.13 Variant Scripts (VSCRIPTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
8.7.1.13.1 Variant Script (VSCRIPT)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
8.7.1.13.1.1 Variant Script Name (VSNAME)
8.7.1.13.1.2 Variant Script Position Offset (VSOFFSETX,
VSOFFSETY) . . . . . . . . . . . .*. 36
8.7.1.13.1.3 Variant Script Anamorphic Scale Factors (VSSCALEX,
VSSCALEY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
8.7.1.14 Recommended Minimum Alignment Line-to-Line Spacing
Distance (MINLINESP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
8.7.1.15 Recommended Minimum and Maximum Anamorphic Scale
. . . . . . . . . . . . . . . . . 37
Factors (M I NANASCALE, MAXANASCALE)
. . . . . . . . . . . . . . . . . . . . . . 38
8.7.1.16 Nominal Alignment Mode (NOMALIGN)
8.7.1.17 Alignment Modes (ALIGNMODES) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
8.7.1.17.1 Alignment Mode (ALIGN)
. . . . . . . . . . . . . . . . . . 39
8.7.1.17.1.1 Alignment Mode Name (ALIGNNAME)
8.7.1.17.1.2 Alignment Line Position Offset (ALIGNOFFSETX,
40
ALIGNOFFSETY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.7.1.17.1.3 Alignment Mode Anamorphic Scale Factors
(ALIGNSCALEX, ALIGNSCALEY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
8.7.1.18 Copy Fit Techniques (COPYFITS)
8.7.1.18.1 Copy Fit Technique (COPYFIT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
. . . . . . . . . . 42
8.7.1.18.1.1 Copy Fit Technique Name (COPYFITNAME)
. . . . . . . . . . . . . . . . 42
8.7.1.18.1.2 Copy Fit Measure (COPYFITMEASURE)
8.7.1.19 Design, Recommended Minimum and Maximum Wordspace
Adjustments (DSNWORDADD, DSNWORDAMPL,
MINWORDADD, MINWORDAMPL, MAXWORDADD,
MAXWORDAMPL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8.7.1.20 Design, Recommended Minimum and Maximum Letterspace
Adjustments (DSNLETTERADD, DSNLETTERAMPL,
MINLETTERADD, MINLETTERAMPL, MAXLETTERADD,
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
MAXLETTERAMPL)
8.8 Specification of font resource glyph metrics properties
(GLYPHMETRICS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
8.8.1 Glyph Metric (GMETRIC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.8.1.1 Glyph Name (GNAME) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.8.1.2 Glyph Position and Escapement Points (PX, PY, EX, EY) 45

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ISO/IEC 954%l:lSSl(E)
46
8.8.1.3 Glyph Extents (EXT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.8.1.4 Glyph Ligature Relationships (LGS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
8.8.1.4.1 Ligature (LG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
8.8.1.4.1.1 Ligature Name (LGN) . . . . . . . . . . . . . . .m. 48
8.8.1.4.1.2 Ligature Successor Names (LGSN) . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.8.1.5 Glyph Pairwise Escapement Adjustments (PEAS) . . . . . . . . . 49
8.8.1.5.1 Pairwise Escapement Adjustment (PEA) . . . . . . . . . . . . . . . . . . . . . 49
. . . . 50
8.8.1.5.1.1 Pairwise Escapement Adjustment Name (PEAN)
8.8.1.5.1.2 Pairwise Escapement Adjustment (PEAX, PEAY) . . . . 50
8.8.1.5.1.3 Seetor-Pairwise Escapement Adjustment Extents
(SPEAFORWDX, SPEAFORWDY, SPEABACKWDX,
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .“. 51
SPEABACKWDY)
8.8.1.6 Class-Pairwise Escapement Adjustment Class Indicator
(CPEAI) . . . . . .*. 52
8.8.1.7 Escapement Adjustment Indicator (EAI) . . . . . . . . . . . . . . . . . . . . . . . . . 53
8.8.1.8 Minimum and Maximum Adjusted Escapement MINEX,
MINEY, MAXEX, MAXEY) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Annexes
55
A Typeface design grouping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
a
n F
D t-onr concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
75
B.l General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
B.2 Font resource environment . 76
B.2.1 Font production . 76
B.2.2 Font resource installation, storage and access . 76
B.3 Application environment . 77
8.3.1 Text processing Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
B.3.2 Document processing
B.3.2.1 Document editing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
B.3.2.2 Document formatting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
B.3.2.3 Document presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
.................................................... ............ 78
B.3.3 Font referencing
B.3.4 Glyph referencing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
78
B.3.5 Glyph positioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
vi

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ISO/IEC 9541=1:1991(E)
8.3.6 Glyph shape presentation .
79
Alphabetical index .
80
VII

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ISO/IEC 9541=1:1991(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the Inter-
national Electrotechnical Commission) form the specialized System for
worldwide standardization. National bodies that are members of ISO or
IEC participate in the development of International Standards through
technical committees established by the respective organization to deal
with particular fields of technical activity. ISO and IEC technical commit-
tees collaborate in fields of mutual interest. Other international organiza-
tions, governmental and non-governmental, in liaison with ISO and IEC,
also take patt in the work.
In the field of information technology, ISO and IEC have established a joint
technical committee, lSO/IEC JTC 1. Draft International Standards adopted
by the joint technical committee are circulated to national bodies for vot-
ing. Publication as an International Standard requires approval by at least
75 % of the national bodies casting a vote.
International Standard lSO/IEC 9541-1 was prepared by Joint Technical
Committee ISO/1 EC JTC 1, Information technology.
lSO/IEC 9541 consists of the following Parts, under the general title In-
forma tion technology - Fon t in forma tion in terchange:
- Part 1: Architecture
- Part 2: In terchange Format
tion
- Part 3: Glyph shape represen ta
- Part 4: Applica tion-specific requiremen ts
Part 1 of lSO/IEC 9541 specifies the architecture of a font resource, i.e.,
the font description, font metrics, glyph description and glyph metrics
properties required for font references and the interchange of font re-
sources.
Part 2 of lSO/IEC 9541 specifies the interchange formats for font infor-
mation, and the minimum subsets of that information required for inter-
Change.
Part 3 of lSO/IEC 9541 specifies the architecture and interchange formats
for glyph shape representations.
Part 4 of lSO/IEC 9541 specifies the architecture and interchange format
extensions for application specific (e.g. typesetting of mathematics) re-
quirements.
Annex A forms an integral part of this part of lSO/IEC 9541. Annex B is for
information only.
. . .
VIII

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ISO/IEC 954%1:1991(E)
Introduction
The use of open networks for the interchange of documents in both Office
and publishing environments has shown the need for a mechanism ena-
bling the interchange of font information.
It is foreseen that publishing and Office technologies will merge and that
this development will be facilitated by definition of a Standard font re-
Source architecture and a limited number of Standard font resource inter-
Change formats.

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ISO/IEC 95417l:lSSl(E)
.X

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ISO/IEC 9541=1:1991(E)
INTERNATIONAL STANDARD
Font information
Information technology -
interchange -
Part 1:
Architecture
1 Scope
lSO/IEC 9541 defines a method of naming glyphs and glyph collections, independent of any document encoding
technique; it assumes that one or more methods of associating document encoding techniques with glyph iden-
tifiers used in font resources will be provided by text processing Systems.
This patt of lSO/IEC 9541 specifies the architecture of a font resource, i.e., the font description, font metrics, glyph
description and glyph metrics properties required for font references and the interchange of font resources.
2 Normative references
The following Standards contain provisions which, through reference in this text, constitute provisions of this part
of ISO/IEC 9541. At the time of publication, the editions indicated were valid. All Standards are subject to revision,
and Parties to agreements based on this part of ISO/IEC 9541 are encouraged to investigate the possibility of ap-
plying the most recent editions of the Standards indicated below. Members of IEC and ISO maintain registers of
currently valid International Standards.
ISO 646: 1983, Information processing - ISO 7-bit coded Character set for information interchange.
ISO 3166:1988, Codes for the representation of names of countries.
ISO 6523: 1984, Data interchange - Structures for the iden tification of organizations.
ISO 8824: 1990, Information technology - Open Systems Interconnection - Specification of Abstract Syntax
Notation One (ASN. 1).
Registration procedures for public text
ISO/IEC 9070:1991, Information technology - SGML support facilities -
o wner iden tifiers.
Fon t information interchange - Part 2: Interchange Format.
ISO/1 EC 9541-2: 1991, Information technology -
-.l) , Information technology - Procedure for registration of glyph and glyph collection identifiers.
lSO/IEC 10036:
1) To be published.

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ISO/IEC 9541=1:1991(E)
3 Definitions
For the purposes of this patt of lSO/IEC 9541, the following definitions apply.
31 . alignment line: Imaginary line to which most glyph images of a font seem to align.
32 . current Position: A Point on the presentation surface at which the next glyph representation is to be imaged.
3.3 design size: Absolute size at which a font is designed to be used.
3.4 escapement: Movement of the current Position on the presentation surface after a glyph representation is
imaged.
3.5 escapement Point: A glyph metric; a Point in the glyph coordinate System, to which the current Position on
the presentation surface is usually translated, after the glyph representation is imaged.
3.6 font: A collection of glyph images having the same basic design, e.g., Courier Bold Oblique.
3.7 font family: A collection of fonts of common design, e.g., Courier, Courier Bald, Courier Bald Oblique.
3.8 font metrics: The set
of dimensions and positioning information in a font resource common to all glyph
representations contained in that font resource.
3.9 font reference: The information about a font resource in an electronie document representation, and possible
procedures and Operation s on that information, w ,hich identify or describe the desired font.
3.10 font resource: A collection of glyph representations together with descriptive and font metric information
which are relevant to the collection of glyph representations as a whole.
3.11 font size: A scalar reference size relative metrics, glyph shapes and glyph metrics are
to which most font
specif ied.
3.12 glyph: A recognizable abstract graphic Symbol which is independent of any specific design.
3.13 glyph collection: An identified set of glyphs.
3.14 glyph coordinate System: A two-dimensional Cartesian coordinate System within which glyph shapes,
glyph metrics, and font metrics are defined.
3.15 glyph image: An image of a glyph, as obtained from a glyph representation displayed on a presentation
surface.
3.16 glyph metrics: The set of information in a glyph representation used for defining the dimensions and pos-
itioning of the glyph shape.
3.17 glyph representation: The glyph shape and glyph metrics associated with a specific glyph in a font re-
Source.
3.18 glyph shape: The set of information in a glyph representation used for defining the shape which represents
the glyph.
3.19 kern: The extension of a glyph shape beyond its Position Point or escapement Point.
3.20 Position Point: A glyph metric; a Point in the glyph coordinate System, usually translated to the current
Position on the presentation surface before the glyph shape is imaged.
3.21 posture: The extent to which the shape of a glyph or set of glyphs appear to incline, including any conse-
quent design or form Change.
graphics display, etc.),
3.22 presentation surface: A virtual rep resentati on of a presentation medium (Page,
be imaged.
maintained by the presentation process, on which a lh shapes are to
11 glYP
2

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ISO/IEC 9541=1:1991(E)
3.23 proportionate width: The ratio of a glyph’s or set of glyphs’ escapement to font height.
3.24 Stern: The major stroke of a glyph shape.
3.25 weight: The ratio of a glyph’s or set of glyphs’ stem width to font height.
3.26 writing mode: An identified mode for setting of text in a writing System, usually corresponding to a nominal
escapement direction of the glyphs in that mode, i.e., left-to-right, right-to-left or top-to-bottom.
4 Notation
An extended Version of Backus-Naur Form (BNF) notation is used to formally define the data types used through-
out this patt of lSO/IEC 9541 in a manner independent of the actual abstract data Syntax used in the font inter-
Change formats. By convention, basic data types are shown in uppercase.
The components of the extended BNF are:
aaa rule syntactic element
---
..- rule definition
element choice (or)
I
element separator
{ .:. ) optional element(s)
( -*- 1 group of elements
( . . . )” 0 to n repeat of element(s) in group
( . . . )+ 1 to n repeat of element(s) in group
II
II
. . . Iiteral element
-
. . . comment
EXAM PLES:
::= b, c: Element a is defined as/composed of the sequence of element b followed by element c (ordered list);
a) a
b) a ::= b 1 c: Element a is defined as either of the elements b or c;
c) a ::= (b 1 c), [d]: Element a is defined as the sequence of containing either of the elements b or c, optionally
followed by the element d;
::= (b 1 c)*: Elem en t a is defined as a sequence of 0 or more instances of either of the elements b or c;
d) a
e) a ::= (b, c, “foo”)+: Element a is defined as a sequence of 1 or more instances of the sequence of the ele-
ments b, c and the literal “foo”.
The formal data type definitions given in clause 8 identify the set of information that must be represented by all
font information interchange formats that conform to this patt of lSO/IEC 9541. There is no requirement that an
interchange format follow the exact organization of data or structures represented in clause 8 , as long as the
general architectural principles of extensibility, backward and forward compatibility are not compromised. Esch
conforming interchange format is free to adopt the most efficient encoding mechanism available in its abstract
Syntax.
In particular, the actual names of properties and property-lists defined in lSO/IEC 9541 do not have to be encoded
directly as data in an interchange format as long as the association between the names and values is maintained.
The fully qualified name of a property or property-list is given by the BNF definition of the structured property name
for each property defined in clause 8 . lt is up to the parsing processes to expand the encoding-specific names into
these fully qualified names for use by encoding-independent interfaces.

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ISO/IEC 9541=1:1991(E)
5 Data types
5.1 General
An elemental data type defines the basic unit of information represented in a font resource for which there is no
further part 1 subdivision. A complex data type is a grouping of elemental data types which are used as basic
building blocks.
This clause defines the elemental and complex data types used throughout this patt of ISO/IEC 9541. The formal
Syntax and method of encoding these data types are defined in the font information interchange format specified
in lSO/IEC 9541-2.
5.2 Properties and property-lists
The principal data type used to represent font resource information is a property. Conceptually, a property is de-
fined to be a name type value tuple, where: name is the unambiguous property name; type is the data type of the
property value; and value is the value of the property, the meaning and interpretation of which is specified by the
property name and the context in which the property is used.
The font resource properties specified in clause 8 of lSO/IEC 9541 include precise definitions of data type. As a
result, the property name is also a specification of the data type and meaning of the corresponding property value.
The data type of non-ISO properties, however, shall be explicitly defined using the elemental and complex data
types defined in this clause.
For example, a property for identifying the font family name used in a font resource might have a property name
FONTFAMILY, whose value is defined to be of data type name, where a particular property value instance might
be Courier.
Proper-ties may be grouped together according to the class of Object they are associated with into property-lists.
A property-list is a set of zero or more properties of an Object, all with property names of the same class. Often
a class of property names is created specifically for the purpose of naming the objects in a particular type of
property-list. For example, the property names WEIGHT and POSTURE might belong to the class of font resource
property names created specifically to name descriptive font resource properties.
The value of a property may be itself a property-list (i.e., the data type is property-list) so that one property-Iist is
effectively nested inside another. In general, this nesting may be repeated indefinitely, so as to permit creation
o
...