This document describes the basic requirements for Indian Languages layout for display purpose. It discusses some of the major layout requirements in first letter pseudo-element, vertical arrangements of characters, letter spacing, text segmentation, line breaking and collation rules in Indic languages.

The minimal requirements presented in this document for Indian languages text layout will also be used in E-publishing and CSS Standard. This documents covers major issues of e-content in Indian languages in order to create standardize format of text layout to address storage, rendering problems, vertical writing, letter spacing, collation, line breaking etc.

It also describes the definition of ABNF(Augmented Backus–Naur Form) based valid segmentation-Indic syllable in order to get the proper display in the browsers. The text segmentation[UAX29] and line breaking [UAX14] algorithms are considered in detail. The CSS & digital publications standards will benefit from this document.

Status of This Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This document describes the basic requirements for Indic script layout and text support on the Web and in eBooks. These requirements provide information for Web technologies such as CSS, HTML and SVG about how to support users of Indic scripts. The current document focuses on Devanagari, but there are plans to widen the scope to encompass additional Indian scripts as time goes on.

The editor's draft of this document is being developed by the Indic Layout Task Force, part of the W3C Internationalization Interest Group. It is published by the Internationalization Working Group. The end target for this document is a Working Group Note.

This document was published by the Internationalization Working Group as a First Public Working Draft. If you wish to make comments regarding this document, please send them to public-i18n-indic@w3.org (subscribe, archives). All comments are welcome.

Publication as a First Public Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. The group does not expect this document to become a W3C Recommendation. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

This document is governed by the 1 August 2014 W3C Process Document.

Table of Contents

1. Introduction

1.1 Indian language complexities

India has large linguistic diversity with 22 constitutionally recognized languages and 12 scripts.This document is currently focused on the Devanagari script. The expectation is that over time its scope will widen to cover additional major scripts from the list below.

The mapping between languages and scripts is complex. Multiple languages may have common scripts, while a language can be written in multiple scripts. Each language and script is unique in nature and cannot be easily replicated, even if they share common characteristics. The orthographic changes may also occur in some languages and adoption of new orthography is a gradual process, thus posing additional challenges.

Serial No. Language Script
1 Hindi Devanagari
2 Sanskrit Devanagari
3 Marathi Devanagari
4 Konkani Devanagari
5 Nepali Devanagari
6 Maithili Devanagari
7 Sindhi Devanagari, Perso-Arabic
8 Bodo Devanagari
9 Dogri Devanagari
10 Bengali Bengali
11 Assamese Bengali
12 Manipuri Bengali, Meetei (Mayak)
13 Gujarati Gujarati
14 Kannada Kannada
15 Malayalam Malayalam
16 Odia Odia
17 Punjabi Gurmukhi
18 Tamil Tamil
19 Telugu Telugu
20 Urdu Perso-Arabic
21 Santhali Ol-Chiki, Devanagari
22 Kashmiri Devanagari, Perso-Arabic

The scripts of South Asia share so many common features that a side-by-side comparison of a few will often reveal structural similarities even in the modern letter forms. They are all abugidas in which most symbols stand for a consonant plus an inherent vowel (usually the sound /a/).The North Indian branch of scripts was, like Brahmi itself, mainly used to write Indo-European languages such as Pali and Sanskrit, and eventually the Hindi, Bengali, and Gujarati languages, though it was also the source for scripts for non-Indo-European languages such as Tibetan, Mongolian, and Lepcha. The South Indian scripts are also derived from Brahmi and, therefore, share many similarities in structural characteristics. For more details visit [South-Asian-Scripts].

The following figure shows the evolution of Indian scripts over a period of times from Brahmi script.

Evolution of Indic Scripts
Fig. 1 Development of Indian Scripts
For more details visit [Evolution-of-Indic-Scripts]

1.2 Basic components of Indian languages

1.2.1 Unicode & CLDR

Unicode is the Universal character encoding standard, used for representing text for information processing. Unicode encodes all of the individual characters used for all the written languages of the world. The standards provide information about the character and their use.

Common Locale Data Repository is the largest standard repository of locale data in the world. It is managed by Unicode Consortium. It provides locale data in an XML format for use in computer applications. It facilitates locale-related information sharing among applications regardless of their domains. Its goal is to provide basic linguistic information for diverse “locales” in an open, interoperable form.

This data is usable for localizing applications.

Some examples of the information that CLDR gathers for languages and territories are:

  • Date formats
  • Time Zones
  • Number formats
  • Currency and its formats
  • Measurement Systems
  • Collation (Sort order) Specification: Sorting, Searching and Matching
  • Translations of names for language, territory, script, time zones, currencies
  • Script and exemplar characters used by a language
  • Calendaring rules, Formats and important dates.

Reference URL: [CLDR]

1.2.2 Unicode Normalization

Unicode normalization[UAX15] is a form of text normalization that transforms equivalent sequences of characters into the same representation. Unicode normalization is important in Unicode text processing applications, because it affects the semantics of comparing, searching, and sorting Unicode sequences

When a unique representation is required , a normalized form of Unicode text can be used to eliminate unwanted distinctions. The key part of normalization is to provide a unique canonical order for visually non distinct sequences of combining characters. Canonical & Compatible Equivalence

Unicode contains numerous characters to maintain compatibility with existing standards, some of which are functionally equivalent to other characters or sequences of characters. Because of this, Unicode defines some code point sequences as equivalent. Unicode provides two notions of equivalence: canonical and compatible.

Canonical equivalence is a form of equivalence that preserves visually and functionally equivalent characters.

The following figure shows the canonical equivalence:

Canonical equivalence in Hindi
Fig. 2 Canonical Equivalence

1.2.3 Unicode Code charts- Devanagari & Devanagari Extended

The following Unicode Character Code chart as per The Unicode Standard, Version 7.0 :

Devanagari and Devanagari extended Code Chart
Fig. 3 Unicode Devanagari and Devanagari extended Code Chart

The Unicode code charts for other Indic scripts are available at [Code-Charts]

1.2.4 Character Set for Hindi

This section provides the basic alphabetic system of Devanagari Script as used for Hindi Consonants, Vowels, Modifiers, Matras, Halant, Nukta etc.

Consonant set

क़ ख़
ड़ ढ़

Vowel set

ं - Anuswara Anuswara, an archinasal, is denoted by a dot  above the letter after which it is to be pronounced. This falls under Nasal category.
ँ -Chandrabindu Candrabindu is pure nasalization as air comes from the nose. It is denoted by a breve with a dot superposed above  the letter after which it is to be pronounced. This falls under Nasal category.
ः - Visarga Visarga(sending forth), denoted by two dots placed one above the other.
ऽ - Avagraha For extra length with long vowels as seen in the Sanskrit text
Halant is used in most writing system to signify the lack of inherent vowel. It is also called virama by Unicode.
Nukta is used in Hindi

For more information See [Draft-Script-Grammar]

2. Indic Syllable boundaries(ABNF Valid segmentation-Proposed solution for layout issues in Indian languages)

2.1 Need for ABNF valid segmentation

ABNF Valid Segmentation based Indic syllable definition is provided here for correct and standardized representation of Indian languages layout. This will address various issues mentioned in the following sections.

This definition will be useful in order to get the uniform display of Indic layout in the browsers, applications, Digital publishing etc.

2.2 ABNF based definition of Indic syllable

Augmented Backus–Naur Form (ABNF) is a meta-language based on Backus–Naur Form (BNF), but consisting of its own syntax and derivation rules. The motive principle for ABNF is to describe a formal system of a language to be used as a bidirectional communications protocol.

V[m] |{CH}C[v][m]|CH

The linguistic definition of Indic syllable has been mapped to ABNF(Augmented Backus–Naur Form) for the purpose of text segmentation, line breaking , drop letter, letter spacing in horizontal text and vertical text representation. The definition has been elaborated , taking Hindi as an example.

The definition is a combination of 3 rules :

Rule 1 : V[m]

Rule 2 : {CH}C[v][m]

Rule 3 : CH (This rule is applicable only at the end of the word)

V(upper case) is independent vowel

m is modifier(Anusvara/Visarga/Chandrabindu)

C is a consonant which may or may not include a single nukta

v (lower case) is any dependent vowel or vowel sign (mātrā)

H is halant / virama

| is a rule separator

[ ] - The enclosed items is optional under this bracket

{} - The enclosed item/items occurs zero or repeated multiple times

2.3 Various Use cases of ABNF based Indic Syllable definition for Hindi language as example

Rule 1 : V[m]

Sl. No. Examples Definition
1 अ, ई, उ V (Vowel) is a syllable
2 अं, उँ, आः V+ Modifier is a syllable

Rule 2 : {CH}C[v][m]

Sl. No. Examples Definition
1 र, क, ज, ल, म Consonant is a syllable
2 प्प, क्ख,च्त, ज्ज्व, त्क्ल, त्स्न Zero or more Consonant + Virama sequences followed by consonant is a syllable
3 र्त, र्त्स, र्त्स्न, र्त्स्न्य, फ़्क़ Zero or more Consonant (Nukta) +Virama  followed by consonant is a syllable
4 र्ता, र्त्स्न्या, फ़्जी, क्या Zero or more consonant+ (Nukta)+ virāma sequences followed by a consonant (+Nukta) followed by a vowel sign is a syllable
5 तः,स्तं, स्त्रँ, स्तः, फ़्ज़ँ  zero or more consonant+ (Nukta)+ virāma sequences followed by a consonant (+Nukta) followed by modifier is a syllable
6 र्त्स्न्या: त्स्न्युं, त्स्न्युँ, फ़्ज़ें,हिं zero or more consonant+ (Nukta)+ virāma sequences followed by a consonant (+Nukta) followed by a vowel sign and modifier is a syllable
7 स्थि, ज्जि, ख्वा Zero or more Consonant +halant sequences followed by a consonant and vowel sign is a syllable

Rule 3 : CH

त्,व्, म्, भ् etc are syllable in Hindi only at the end of the word

Examples of combination of the rules :

1. स्वागतम् - CHCv + C + C + CH has following syllables :

स्वा CHCv
म् CH

2. भरतनाट्यम- C + C + C + Cv + CHC + C

ना Cv
ट्य CHC

3. Text segmentation

A string of Unicode-encoded text often needs to be broken up into text elements programmatically. Common examples of text elements include what users think of as characters, words, lines (more precisely, where line breaks are allowed), and sentences. The precise determination of text elements may vary according to orthographic conventions for a given script or language. The goal of matching user perceptions cannot always be met exactly because the text alone does not always contain enough information to unambiguously decide boundaries. For example, the period (U+002E FULL STOP) is used ambiguously, sometimes for end-of-sentence purposes, sometimes for abbreviations, and sometimes for numbers. In most cases, however, programmatic text boundaries can match user perceptions quite closely, although sometimes the best that can be done is not to surprise the user. Word boundaries are used in a number of different contexts. The most familiar ones are selection (double-click mouse selection, or “move to next word” control-arrow keys), and “Whole Word Search” for search and replace. They are also used in database queries, to determine whether elements are within a certain number of words of one another . Some special sentence boundaries like the double poorna virama, possibly with numbers (as in Sanskrit text, shlokas etc.) Grapheme cluster boundaries are important for collation, regular expressions, UI interactions (such as mouse selection, arrow key movement, backspacing), segmentation for vertical text, identification of boundaries for first-letter styling, and counting “character” positions within text. [UAX29]

Solution for word boundaries:
User-percieved characters boundaries should be based on tailored Grapheme Cluster Boundaries to conform Indic Syllable definition

In case of Devanagari phrase separator called Danda or purnaviram (।) and double danda (।।: used to mark end of the verse),In some of the browsers ending word is selected with purnaviram on double-click while in some browsers Danda is selected as a separate. It is recommended that line should not begin with purnaviram/Danda and double danda. So the properties of Danda should be same as the properties of FullStop or other punctuation marks so that new line should not begin with Danda and double danda.

For others characters, the text segmentation should be done as Indic syllable.

4. Line breaking

When inline-level content is laid out into lines, it is broken across line boxes. Such a break is called a line break. In most writing systems, in the absence of hyphenation a line break occurs only at word boundaries. Many writing systems use spaces or punctuation to explicitly separate words, and line break opportunities can be identified by these characters. Line breaking, also known as word wrapping, is the process of breaking a section of text into lines such that it will fit in the available width of a page, window or other display area.

4.1 Hyphenation

There are different cases of hyphenation, some of the cases are given below :

Case 1 : Hyphens are commonly used in Copulative compounds words in Hindi language. Hindi has both prefixes and suffixes which are joined to words with a hyphen.

नर-नारी, लाभ- हानि, माता-पिता, ऊंच - नीच

Case 2: Single word can breaks at the end of the line at Indic syllable level using hyphen

In the below screenshot, words आकर्षण and विज्ञापन not follow Indic syllable definition in some of the browsers.

Example of Line breaking

4.2 Guiding principles of Line breaking for Indian languages

In Indic writing system , it is preferred that line breaks at word boundaries ,if required following principles may be adhered :

Rule 1: New line cannot begin with following symbols/Punctuation marks. Also these should be retain with the associated text

Rule 2: The definition of Indic syllable may be used to break the line and a hyphen should be at the breaking point so that word can be read intuitively

Rule 3: The hyphenated words can be broken at the hyphen e.g.:

Rule 4: Expression with mathematical symbol should be treated as single unit so that at the end of the line expression should not breaks at operator level

Rule 5: Breaking should not be allowed at numerical values such as currency values, year etc. e.g.

“100.00” or “10,000”, nor in “12:59”

5. Requirements for Indic Layout

5.1 First Letter

Drop initial is a typographic effect emphasizing the initial letter(s) of a block element with a presentation similar to a 'floated' element. The drop initial effect may also be used for writing systems which use different alignment strategies. For example, in Devanagari the hanging baseline may be preferred. In that case the primary connection point connects the text-after-edge of the initial letter with the text-after-edge of the nth line, but the secondary connection point connects the hanging baselines of the initial letter and the initial line.

Example of Drop letter in Hindi

Indic script behavior in First-letter in non -Latin scripts relates to syllables, rather than individual letter forms. In the Hindi word स्थिति ('sthiti') the sequence of characters in the first syllable is as stored in memory is as shown at the top of fig.4

Note how the vowel sign appears to the left of the first character, not the third. There are three grapheme clusters here. The first includes the SA+VIRAMA,THA+I and T+II. We see that the styling is done on the basis of the syllable, not the first character. A syllable includes a base consonant and any combination of the following characters in the text stream:


The detailed definition of Indic syllable is describe in section 2.

Example of First letter in Hindi
Fig. 4 Styling of first Letter

Here is some of the examples of first highlighted letter based on Indic syllable definition.

Example of First letter in Hindi
Fig. 5 Example

5.2 Letter Spacing

In styling issues like horizontal spacing, the spacing between characters like C E R T I F I C A T E, the space is given between the every character in case of English. But in case of Indian language, the space needs to be introduced after each syllable for correct representation.

For letter spacing in Indian languages it is recommended that spacing should follow Indic syllable definition.

Here is the some examples of letter spacing that based on definition :

1. अं त र्रा ष्ट्री य क र ण 2. स्वा ग त म् 3. सु स ज्जि त 4. स म्प्र ति

5.3 Vertical arrangements of characters

In vertical arrangement of characters writing each character on a new line may not be suitable in Indian languages. The vertical arrangements of characters are sometimes used in Indian texts. In order to form correct arrangements, it is preferred to follow tailored grapheme cluster approach. Variations of vertical arrangement of the characters in Hindi is represent below :

Variations in vertical arrangements

Example of Vertical arrangements in Hindi
Fig. 6 Variations in vertical arrangements

Vertical representation of the word 'स्वागतम्' based on Indic Syllable definition:


5.4 Collation

Collation is one of the most important features for Indic languages . It determines the order in which a given culture indexes its characters. This is best seen in a dictionary sorting order where for easy search words are sorted and arranged in a specific order. Within a given script, each allo-script may have a different sort-order. Thus in Hindi the conjunct glyph क्ष is sorted along with क , since the first letter of that conjunct is क and on a similar principle ज्ञ is sorted along with ज . The same is not the case with Marathi and Nepali which admit a different sort order.

Different scripts admit different sort orders and for all high end NLP applications. Sorting is a crucial feature to ensure that the applications index data as per the cultural perception of that community. In quite a few States, sort order is clearly defined by the statutory bodies of that state and hence it is crucial that such sort order be ascertained and introduced in the document .

The order(left to right) as given below is pertinent to sorting by a computer program and is compliant with CLDR as laid down by Unicode.

























































\U0944 \U0945






Following is the sort order of Consonant 'क'

कँ कं कः का कि की कु कू कृ के कॅ
कै को कॉ कौ क् क़          

6. Contributors

Serial No. Name Organization
1 Manoj Kumar Jain DeitY
2 Gautam Sengupta University of Hyderabad
3 Girish Nath Jha JNU
4 Rajeev Sangal IIT Varanasi
5 Dipti Misra Sharma IIIT Hyderabad
6 R K Sharma Thapar University
7 Rajat Mohanty IIT Bombay
8 Venkatesh Choppella IIIT Hyderabad
9 Soma Paul IIIT Hyderabad
10 M D Kulkarni C-DAC Pune
11 Panchanan Mohanty University of Hyderabad
12 G. Uma Maheshwar Rao University of Hyderabad

A. References

A.1 Normative references

Unicode CLDR. URL: http://cldr.unicode.org
Unicode Code Charts. URL: http://www.unicode.org/charts/
Draft-Scrip-Grammer Devanagari. URL: http://tdil-dc.in/index.php?option=com_vertical&task=view-article&article_id=149&lang=en
Indic Scripts. URL: http://www.ciillibrary.org/Sites/Photography/PhotographyHome.html
Unicode Technical note#10 : South Asian Scripts. URL: http://www.unicode.org/notes/tn10/
Unicode Line Breaking Algorithm. URL: http://www.unicode.org/reports/tr14/
Mark Davis; Ken Whistler. Unicode Normalization Forms. 31 August 2012. Unicode Standard Annex #15. URL: http://www.unicode.org/reports/tr15
Grapheme Cluster boundaries. URL: http://www.unicode.org/reports/tr29/