Enhanced Global Language Support(EGLS) in EPUB

Subgroup Recommendation October 17, 2010

Table of Contents

1. Introduction

2. Recommendations

3. Introduction to and Status of the Referred Specifications

3.1 CSS Writing Modes Module Level 3

3.2 HTML5

3.3 CSS Text Level 3

3.4 Alternate Style Tags

Appendix: Contributors

1. Introduction

This document provides recommendations from the EGLS sub-group to the EPUB 3.0 WG. These recommendations are intended to provide solutions to the requirements shown in the EGLS requirements wiki page

These recommendations are based on the consensus reached in the EGLS face-to-face meeting in Taipei 2010-10-05/06. Rationales for each recommendations can be found in either the solution wiki or the minutes of the meeting. The mintues of the meeting will be provided in the very near future.

2. Recommendations

Recommendation A

Details of the interaction between these two mechanisms will be provided by Takeshi Kanai and Koji Isshi.

Recommendation B1

Recommendation B2

Recommendation C

Note: hanging-punctuation, a property in CSS Text Level 3, will be marked as "at risk". + +

Recommendation D1

Recommendation D2

Recommendation D3

Recommendation D4

Recommendation E

Recommendation F

Recommendation G

Note: This makes the interpretation of metadata where multiple elements are allowed ambiguous. For example, it is not clear whether there are two contributors or one with two name varaints. The resolution of this issue is deferred to the metadata subgroup.

Recommendation H

Recommendation I

Note: If css3-fonts is not ready, this is effectively replacing an existing normative requirement in EPUB2, not adding anything new. See also Section 3.5.

Recommendation J

3.0: Introduction to and Status of the Referred Specifications

3.1: CSS Writing Modes Module Level 3

This module defines support for various international writing directions, such as left-to-right (e.g., Latin scripts), right-to-left (e.g., Hebrew or Arabic), bidirectional (e.g., mixing Latin with Arabic) and vertical (e.g., Asian scripts). It extends properies that are long-existing in CSS2 such as unicode-bidi. It is essential to enhanced global language support.

Although this specification is not yet published by W3C as a working draft, the editor (fantasai) is optimistic about the future of this spec since there's an exsisting implementation by Antenna House and an ongoing implementation by the Webkit team. Two interoperable implementations greatly help this spec towards a W3C recommendation, since one of the criteria for a W3C recommendation is two interoperable implementations.

The relevant solutions to the requirements are: Two Styles of Vertical Writing, Writing Mode of Captions and Table Entries, Providing Reasonable Fallbacks to Horizontal Writing, One by One, Tate-chu-yoko.

3.2: HTML5

The relevant solutions to the requirements are: Mono Ruby, Jukugo-ruby, Group-ruby, Bopomofo Ruby (Zhuyin Fuhao).

3.3: CSS Text Level 3

This CSS3 module defines properties for text manipulation and specifies their processing model. It covers line breaking, justification and alignment, white space handling, text decoration and text transformation. Line breaking and justification are highly area-dependendent (CJK area, Southeast Asia, Arabic, Mongolian are covered) and hence this specification certainly adresses the need of EGLS.

This specification is now very active. It was published as a W3C published draft very recently. It is expected to reach the state of Candidate Recommendation in early 2011.

The relevant solutions to the requirements are: One by One, Line-start and Line-end Prohibition Rules, Unbreakable Character Sequences, Hanging Punctuations, Non-separating Characters, Emphasis Dots.

3.4: Alternate Style Tags

This module defines a pattern for tagging alternate style sheets using a microformat, where certain values of the class attribute on a (X)HTML link element are standardized. It can be used to define standardized classes that can be hooked into the browser UI. Sample use cases include horizontal-vertical layout switches in Japanese Ebook readers; automatically selecting high-contrast styles; and other accessibility concerns.

This is a simple extenstion to the existing alternate style mechanism in (X)HTML, and its inplementation cost should be pretty low. This spec does not currently belong to a standard body. Makoto Murata might bring this specification to the EPUB Working Group.

The relevant solutions to the requirements are: Principal Writing Mode, Providing Reasonable Fallbacks to Horizontal Writing, Providing Optimal Layouts for more than one Principal Writing Mode, Announcing non-optimality.

Appendix: Contributors

This document has been developed by Enhanced Global Language Support sugroup of the International Digital Publishing Forum (IDPF)'s EPUB working group. Group members and face-to-face meeting attendees are listed as follows: