This document describes or points to requirements for the layout and presentation of text in languages that use the Tibetan script. The target audience is developers of Web standards and technologies, such as HTML, CSS, Mobile Web, Digital Publications, and Unicode, as well as implementers of web browsers, ebook readers, and other applications that need to render Tibetan script text.
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This document describes the basic requirements for Tibetan script layout and text support on the Web and in eBooks. These requirements provide information for Web technologies such as CSS, HTML and digital publications about how to support users of Tibetan script languages. Currently the document focuses on the Tibetan script as used for Tibetan script. The information here is developed in conjunction with a document that summarises gaps in support on the Web for Tibetan script.
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1. Introduction
1.1 Contributors
The initial information in this document was provided by Richard Ishida.
1.2 About this document
The aim of this document is to describe the basic requirements for Tibetan script layout and text support on the Web and in eBooks. These requirements provide information for Web technologies such as CSS, HTML and digital publications, and for application developers, about how to support users of the Tibetan script.
The document focuses on typographic layout issues. For a deeper understanding of Tibetan script using the Tibetan script and how it works see Tibetan Orthography Notes, which includes topics such as: Phonology, Vowels, Consonants, and Numbers.
This document should contain no reference to a particular technology. For example, it should not say "CSS does/doesn't do such and such", and it should not describe how a technology, such as CSS, should implement the requirements. It is technology agnostic, so that it will be evergreen, and it simply describes how the script works. The gap analysis document is the appropriate place for all kinds of technology-specific information.
1.3 Gap analysis
This document should be used alongside a separate document, Tibetan script Gap Analysis, which describes gaps in support for Tibetan script on the Web, and prioritises and describes the impact of those gaps on the user.
To complement any content authored specifically for this document, the sections in the document also point to related, external information, tests, GitHub discussions, etc.
The document Language enablement index points to this document and others, and provides a central location for developers and implementers to find information related to various scripts.
The W3C also has a repository with discussion threads related to the Tibetan script, including requests from developers to the user community for information about how scripts/languages work, and a notification system that tracks issues in W3C working groups related to the Tibetan script. See a list of unresolved questions for Tibetan script experts. Each section below points to related discussions. See also the repository home page.
2. Tibetan script overview
Tibetan can be written using two different styles: དབུ་ཅནdbu canwith a head, the block style of the Tibetan script used in print, pronounced u.cen; and དབུ་མེདdbu medheadless, the cursive style of the Tibetan script used in shorthand and calligraphy, pronounced u.me. This page concentrates on the former. Pronunciations are based on the central, Lhasa dialect.
Historically, Tibetan text was written on loose-leaf sheets called pechas, ( དཔེ་ཆ pé.t͡ɕʰá book, scripture ). Some of the characters used and formatting approaches are different in books and pechas.
Tibetan text runs left to right in horizontal lines.
Words boundaries are not indicated. However, Tibetan words are made up of one or more units called tsheg-bar which are basically equivalent to phonological syllables. The tsheg-bar units are separated using ་ U+0F0B TIBETAN MARK INTERSYLLABIC TSHEG.
These tsheg-bar units are composed of structural elements that include vowel signs and consonants used as prefixes, root characters, subscripts, superscripts, suffixes, and secondary suffixes. A common realisation includes a stack and additional consonants to either side of the root consonant. These may indicate syllable-final consonant sounds, but more often than not they qualify or modify the root value, and are not associated with their nominal sound value. The actual pronunciation of Tibetan is usually much more simple than a typical romanisation would suggest. For example, the word བཀོད kǿː to create is transcribed as bkod.
Figure 1The single-syllable word cy᷈ː string with an initial stack of three consonants plus a vowel sign. followed by a suffix consonant (to the right).
To write the sounds of the standard Lhasa dialect, Tibetan uses 28 consonant letters (plus their subjoined forms). 6 more letters are used to write Sanskrit.
A distinguishing feature of Tibetan is the set of separate code points for subjoined consonants, used to create consonant stacks. Of the 77 combining characters in the Tibetan block, 48 represent subjoined consonant forms. Unlike many other Indic scripts, the modern Tibetan orthography doesn't use a virama to create stacks.
Tibetan is an abugida with one inherent vowel. When writing the Lhasa dialect, other post-consonant vowels are represented using 4 vowel signs, all combining marks.
There are no pre-base, circumgraph, or multipart vowels in the Tibetan used to write the Llasa dialect (though there are when writing in Sanskrit).
Standalone vowels are written by adding vowel signs to either འ U+0F60 TIBETAN LETTER -A or ཨ U+0F68 TIBETAN LETTER A, depending on the tone.
Sanskrit vowels written in Tibetan use additional vowel signs and combining marks, some of which represent diphthongs, and some of which form circumgraphs or multipart characters, depending on the encoding.
Tone is indicated by the choice of root character and/or its associated prefixes and superscripts.
Modern Tibetan writing uses few punctuation marks or symbols, but the Tibetan script block in Unicode contains many of these.
Tibetan has its own set of numbers.
2.1 Tibetan Syllables
The following diagram shows characters in all of the syllabic positions, and lists the characters that can appear in each of the non-root locations. The two-syllable word in the example is འགྲེམས་སྟོན 'grems-ston ɖɹemton exhibition.
