W3C Working Draft 11-May-1998
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Norman Walsh <nwalsh@arbortext.com>

Status of this document

This work is part of the W3C Style Activity. For information about XSL, see http://www.w3.org/Style/XSL.

This is a W3C Working Draft for review by W3C members and other interested parties. It is a draft document and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". A list of current W3C working drafts can be found at http://www.w3.org/TR.

Table of Contents

General Formatting Issues
Columns, Floats, Keeps, etc.

This document gives a list of requirements we consider to be in scope for XSL in general with no reference to timing or target version. This document makes no statement about what specific requirements will be addressed in any particular Working Draft or version of XSL.

In accordance with good language design practice, the full set of requirements are presented so that, at every step in the design process, design choices are made taking the full set of requirements into account, rather than just a subset of those requirements currently being met. It is the XSL WG's expectation that initial drafts/versions of XSL will address only a subset of these requirements.

When reviewing these requirements, keep in mind that XSL is required to perform equally well in batch and interactive environments. These environments run from purely batch formatting at one end of the spectrum, through interactive browser environments, up to structured editors where XSL is used to guide the online presentation of an XML instance while it is being modified.

It must be noted that this list represents a list of requirements which it must be possible to express in XSL. It is not our intent to suggest that every XSL processor must support every feature described here (although processors should handle requirements they cannot satisfy in some more-or-less graceful way).

Within each section, requirements are listed alphabetically, not in any priority order.

General Formatting Issues

Absolute/relative positioning, Layering, and Transparency

Ability to specify absolute/relative positioning of areas on the presentation medium and/or with respect to each other, incuding specification of Z-order for overlapping areas and handling of transparency.

Alignment of scripts and baseline shifts

Support for automatic alignment of text from multiple scripts with different alignment rules. Ability to handle sub- and super-scripts.


Support for identifying and including encapsulated, animated objects.


Linking hotspots to items in the flow of text. Another aspect would be manipulating presentation of text within a CGM graphic.


Ability to specify parameters that can be adjusted to make text fit in a specified area.

Cropping and Scaling of Images

Support for specification of cropping and scaling of images (and related issues such as bleeds).


Support for/handling of the issues related to cross–references. For example, page numbers and auto-numbering, document wide variables (release, version, etc.), explicit textual cross–references, etc.

Dictionary-style headers

Support for headers or footers whose content changes depending on the placement of page breaks (in print media). For example, in an English dictionary, the page header generally contains the first and last words defined on that page.

Drop/raised cap

Support for drop and raised caps.

Formatting changes at non-tag boundaries

Ability to change formatting at arbitrary places in the source document.

Hanging punctuation

Support for punctuation that hangs outside the right or left text margin. In English writing, hanging punctuation would place commas and periods at the ends of lines in a paragraph just past the right-most text margin, for example.


Basic running headers and footers (changing on chapter boundaries, page numbers, etc.)


Ability to specify hyphenation information.

Hyperlink addressing

Ability to specify presentation characteristics of link ends defined by XLink elements.

Indents (start/end and right/left)

Specification of starting and ending indents on the display medium. In English writing, the left margin is the start margin and the right margin is the end margin.


Issues related to indexing: sorting, collating, coalescing. See also cross references. (Easy things should be easy.)

Inline (horizontal) keeps

Ability to specify that certain inline markup cannot be broken across lines. Issues: interaction with justification and non-breakable spaces.

Justification/Word and Letter Spacing

Justification/spacing policy controls as per DSSSL.

Kerning (pair, track, ...)

Support for some/all of the following: ability to enable/disable font kerning metrics, specify font kerning overrides, specify track kerning, automated pair kerning, manual kerning, etc.


Automatic leading and manual control. Relates to ability to address elements below the tag boundary (lead this line more or less tightly).


Support for easy construction of a wide variety of types of lists. (Easy things should be easy)


Side-notes, margin illustrations, etc.


Ability to specify margins. Harmonization of DSSSL/CSS models.

Non-rectangular Areas

Ability to format text in/around non-rectangular areas.

Page dynamics

Support for specification of designs across different aspect ratios, form and media factors using a single stylesheet.

Para breaks

Explicit control over paragraph breaking. (e.g., Suspend and resume a paragraph around an embedded object?)

Persistent headers/footers w/scrolling body

Ability to specify headers and/or footers that should be fixed at the borders of a scrolling text area. This would provide the functionality most commonly achieved with frames in HTML browsers today.


Page fidelity is neither a requirement nor a goal. Presented with the same document and the same stylesheet, a given renderer should always produce the same results. Different renderers should produce similar results.

Rule corners/boxes/borders

Ability to specify square, rounded, and other end-of-rule treatments on rules. Ability to specify the treatment of box corners and border edges.


Flowing text around rectangular areas.

Sorting/Collating/Data processing

Support for sorting and collating data (for example in index entries, but more generally wherever it is required for proper presentation). Support for other sorts of data-processing functions may be required as well.

Support for Structured Data

XSL will be called upon to process data which is more highly structured, and differently structured, than traditional text documents (for example, calendars, schedules, stock prices, etc.). XSL must provide sufficient functionality to adequately style such documents.


Support for the table models of CSS and DSSSL. Ability to easily format popular source table models such as HTML and CALS.

Tables of Contents

Support for construction of ToCs and other document views. (Easy things should be easy).

Text and images (bitmap/vector)

Handle scaling issues.


Background repeat of graphic background.

Columns, Floats, Keeps, etc.

Column balancing

Ability to specify that columns should be balanced on paged media.


Support for vertical floats, including the ability to control position (top, middle, bottom) and to specify the constraints on how far a float may move from the point of origin.

Footnotes (single/multi column)

Support for footnotes in multicolumn text is non-trivial. Ability to specify footnote area, footnote placement, and treatment of very long footnotes.

Multiple columns (equal width)

Support for multiple columns of equal width (with equal width gutters).

Multiple columns (mixed width)

Support for multiple columns of unequal width (or gutters of unequal width).

Side-by-side columns

Ability to specify multiple columns where the flow is side-by-side rather than top to bottom. (To align original text and translated text, for example).

Vertical keeps

Ability to specify vertical keeps (regions or distances within which a page and/or column break may not occur).

Widow/orphan control

Ability to specify handling of widows and orphans.


Ability to capture a character outline

Capturing a character outline would allow text to flow around the actual shape of a glyph.

Character selection and substitutions (glyph selections, ligatures, small style, etc.)

Ability to specify and/or select individual glyphs or ligatures, fonts and font substitutions, and font styles.

Dynamic font downloading (web fonts, performance of dynamic fonts)

Support for high-speed font access (construction of fonts on-the-fly, fast substitutions, etc.).

Font selection identification and related full font substitution services

Support for a comprehensive set of font selection and substitution parameters.

Interrogate font metrics/Calculate longest line

Ability to determine character and/or string lengths. Support for text formatting that is contingent on line length (for example, make the first line of a paragraph small caps).

Text along a curve (move to a formatter issue)

Ability to format text along the path of a bezier (or other type of) curve.

Units of measurement

Specification of both absolute and relative units of measurement (pts, picas, inches; ems, ens, exes, etc.)


Colors Specification


Ability to specify fills and shading (specification of color and gradients in flood, linear, circular, etc. fills).


Support for masks (e.g., fill all of a specified area except for the area defined by a second parameter or image)..


Support for layers with varying degrees of transparency.


DSSSL 12.6.26

Support for math is expected to come initially from the math operators defined in section 12.6.26 of the DSSSL Standard.


Support for MathML is anticipated.


Internationalization involves issues of character/glyph sets, line-breaking/hyphenation/justification, and layout issues that go well beyond the basic western typography considerations of most applications.

In most languages there is a significant range between the level of formatting/typography needed for business documents and basic markets vs. the level required for advertising and commercial publishing. Web usage produces an interesting blend, as it doesn't require the full typographic capability needed for print advertising, yet requires much of the design and layout capability.

Date and numbering systems seem to vary by country and by language. Digit and value representations are described in unicode. Date handling is not.

Major language groups are listed with no particular order:

Western European and related languages

This language group includes most North & South American, African business, Latin, and western European languages.


Chinese, Korean, & Vietnamese (iconic form)

The requirements of these languages are subsets of the requirements of Japanese, though they have different character sets.


This is a script language that is unique in a number of ways:


Though stylistically simpler than Arabic, Hebrew carries many similar characteristics (Mixed writing directions, glyph variants, etc.). If you satisfy the requirements for western Europe and Arabic, you have satisfied most of those of Hebrew.

Eastern Europe and Russian republics

Except for character sets, there are no known requirements for these languages that are not covered by those of western Europe. We need to confirm this.

India and Indic rim



Southeast Asia and South Pacific

Infrequently used, dead, and archaic languages

There are a number of issues regarding infrequently used, dead, and archaic languages that we might want to support for academic studies and literature:


“Query Expressions”

Ancestors, children, siblings, attributes, content, disjunctions, negation, enumerations, computed select based upon arbitrary query expressions.

Arithmetic Expressions

Arithmetic, simple boolean comparisons, boolean logic, substrings, string concatenation.

Data Types

Scalar types, units of measure, Flow Objects, XML Objects

Side effects

No global side effects.

Standard Procedures

The expression language should have a set of procedures that are builtin to the XSL language. These are still to be identified.

Types of Scripting

User Defined Functions

For reuse. Parameterized, but not recursive.



Support for defining the interactive response to certain behavioral and user-interface events such as mouse-clicks and loading and unloading of a document.


Support for defining “input elements” of a document (e.g. HTML forms).

Interactive Response

Support for defining the interactive response of all visible objects. Support for renderer-meaningful mechanisms and language for defining the action that occurs upon interaction.

Look and Feel

Support for defining the look and feel of the input objects (i.e., mechanisms to bind the abstract input elements to concrete presentational widgets).


Aural stylesheets

Support for audio (aural) stylesheets.

XSL must support accessibility mechanisms

Additional accessibility support will be defined.


Extensibility at the object level

Possibly provide the ability to specify additional Flow Objects or XML Objects

Extensibility at the property/characteristic level

Possibly provide the ability to specify additional characteristics on objects.


Associating Stylesheets and Documents

Ability to specify the stylesheet(s) that apply to a particular document (or class of documents)

Cascading (publisher/consumer)

Specify how author/reader stylesheets can cascade.

Modularity of Stylesheets

Allow stylesheets to be composed (possibly dynamically) from multiple individual stylesheet fragments.

Selective override

Specify the selection of criteria for determining what stylesheet (or what part of a stylesheet) overrides another. Handling of specificity issues.


Crop marks, registration marks

Ability to specify formatting of areas outside the typical display area.

Grain direction/Stock specification

Ability to specify stock and grain direction for print media.


Ability to specify the order and nature of imposition (the process of constructing signatures from pages) with the focus on the types of imposition supported by standard laser printers.

Job control

Ability to specify job control for specific devices.

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