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for e-Government
Logo A-SIT

The Austrian Citizen Card

Standardised Viewer Format


Document information

Designation

Standardised viewer format for the Citizen Card Environment of the Austrian Citizen Card

Brief designation

Standardised viewer format

Version

1.2.1

Date

2005-03-01

Document class

Convention

Document status

Recommendation

Short Name

This document specifies the standardised viewer format for the Austrian Citizen Card, based on XHTML 1.1 and CSS 2. It must be possible for the standardised viewer format to be processed and displayed by all Citizen Card Environments.

Authors

Arno Hollosi
Gregor Karlinger

Work group

Federal Chancellery, Federal Staff Unit for ICT Strategy, Technology and Standards

©

This specification is supplied by A-SIT and the Federal Chancellery. It may be used without modification provided that reference is made to this copyright notice. The specification may be expanded, however any additional material must be clearly identified and the expanded specification must be made freely available.


Table of contents

  1. Introduction
    1. Naming conventions
    2. Keywords
    3. Definitions
  2. Profile of XHMTL 1.1
    1. Restrictions in comparison with XHTML 1.1
      1. Attribute Collections
      2. Core Modules
      3. Applet Module
      4. Text Extension Module
      5. Forms Modules
      6. Table Modules
      7. Image Module
      8. Client-side Image Map Module
      9. Server-side Image Map Module
      10. Object Module
      11. Frames Module
      12. Target Module
      13. Iframe Module
      14. Intrinsic Events Module
      15. Metainformation Module
      16. Scripting Module
      17. Style Sheet Module
      18. Style Attribute Module
      19. Link Module
      20. Base Module
      21. Name Identification Module
      22. Legacy Module
    2. XML schema for the standardised viewer format
    3. Miscellaneous
      1. Comments
      2. Rendering outside the canvas
  3. Profile of CSS 2
    1. Integration of CSS formats in the standardised viewer format
    2. Use of CSS formats by the Citizen Card Environment
      1. Default CSS style sheet
    3. At-rules
      1. @charset
      2. @import
      3. @media
      4. @page
      5. @font-face
    4. CSS selectors
    5. CSS properties
      1. Value specifications
      2. Spacing and borders
      3. Positioning of boxes
      4. Displaying boxes
      5. Visible area in boxes
      6. Generated content, numbering, lists
      7. Page-based media
      8. Colours and background
      9. Fonts
      10. Displaying text
      11. Tables
      12. User interface
      13. Voice output
  4. Images in the standardised viewer format
    1. Integration in the XML signature
      1. Example
    2. Process model for creating and verifying signatures
      1. Creating a signature
      2. Verifying a signature
  5. References
  6. History

1 Introduction

To enable an application to use commands of the Security Layer interface without needing to know the specific underlying implementation (Citizen Card Environment), it is necessary that there should be at least one viewer format that can be processed and displayed by every Citizen Card Environment.

This document specifies this standardised viewer format. The basis for it is provided by the international standards [XHTML 1.1] and Cascading Style Sheets 2 [CSS 2]. Taking this as a starting point, restrictions are defined to ensure that the viewer format is suitable for secure display. For example, link information or dynamic elements such as scripts are not permitted.

Section 2 defines the profile of [XHTML 1.1]. This profile defines the fundamental structure of a document corresponding to the standardised viewer format.

Section 3 defines the profile of [CSS 2], which allows the layout information for a document corresponding to the standardised viewer format to be defined. The CSS information is incorporated in the XHTML structure of the document exclusively by means of the <xhtml:style> element.

1.1 Naming conventions

For better readability, this document dispenses with non-gender-specific formulations. However, the formulations expressly relate to both sexes.

The following name space prefixes are used in this specification to identify the name spaces of XML elements:

Prefix Name space Explanation
xhtml http://www.w3.org/1999/xhtml Elements from [XHTML 1.1]
dsig http://www.w3.org/2000/09/xmldsig# Elements from [XMLDSIG]

1.2 Keywords

This document uses the following keywords to categorise requirements: must, must not, required, should, should not, recommended, may, and optional. The interpretation of these keywords is set down in [Keywords].

Particular attention is drawn at this point to the fundamentally different meaning of should (and its corresponding elements) as opposed to may (and its corresponding elements) (cf. [Keywords], sections 3 and 5).

1.3 Definitions

Instance document
A document that meets the definitions of this specification or that is assumed to meet the definitions of this specification.
must be rejected
This phrase means that an instance document must not be displayed by the viewer component of the Citizen Card Environment. In this case, the Citizen Card Environment must signal an error to the caller.
must not be displayed
This phrase means that a certain part of the instance document (e.g. an attribute value or the content of an element) must not be displayed by the viewer component of the Citizen Card Environment. However, this does not mean that the instance document must therefore be rejected by the Citizen Card Environment.

2 Profile of XHMTL 1.1

This section describes the profile for the XML structure of the standardised viewer format. The structure of this section is based on the modules defined in [XHTML 1.1], section 5: The restrictions in relation to the elements and attributes permitted in the standardised viewer format are specified for each module.

The XML schemas referenced at the end of this section serve as a normative summary of the restrictions. They are based on the mechanism for creating an XHTML dialect suggested in [XHTML MOD]. Instance documents that do not correspond to this schema precisely must be rejected by a Citizen Card Environment.

2.1 Restrictions in comparison with XHTML 1.1

2.1.1 Attribute Collections

Compare [XHTML 1.1], section 5.1.

The title attribute is omitted from the Core attribute collection. The Events, Style and I18N attribute collections are completely emptied. Thus, the Common attribute collection is identical with Core.

2.1.2 Core Modules

Compare [XHTML 1.1], section 5.2.

2.1.2.1 Structure Module

The profile attribute for the head element is omitted. The content model of the head element is changed to (title, style).

The version attribute for the html element is set to the value -//www.buergerkarte.at//DOCUMENT SLXHTML 1.2//DE.

The body and title elements remain unchanged in terms of both the content model and attributes.

2.1.2.2 Text Module

The cite attribute for the blockquote element is omitted.

The br, cite, code, div, em, h1, h2, h3, h4, h5, h6, p, pre, span and strong elements remain unchanged both in terms of content model and attributes.

The Heading and Flow content sets remain unchanged; the Block content set changes to (blockquote|div|p|pre); the Inline content set changes to (br|cite|code|em|span|strong). This means that the abbr, acronym, address, dnf, kbd, q, samp and var elements are not used.

2.1.2.3 Hypertext Module

This module is not used.

2.1.2.4 List Module

This module is used without change.

2.1.3 Applet Module

This module is not used.

2.1.4 Text Extension Module

2.1.4.1 Presentation Module

The hr element remains unchanged both in terms of content model and attributes. The tt, i, b, big, small, sup and sub elements are not used.

This means that the Block content set is expanded to include the hr element.

2.1.4.2 Edit Module

This module is not used.

2.1.4.3 Bi-directional Text Module

This module is not used.

2.1.5 Forms Modules

These modules are not used.

2.1.6 Table Modules

2.1.6.1 Basic Table Module

This module is not used.

2.1.6.2 Table Module

The content model remains the same for all elements.

The summary, width, border, cellpadding, cellspacing, datapagesize attributes and frame und rules attribute groups for the table element are omitted.

The abbr, axis, headers attributes and scope, CellHAlign and the CellVAlign attribute groups for the th and td elements are omitted.

The CellHAlign and CellVAlign attribute groups for the tr, thead, tfoot and tbody elements are omitted.

The span and width attributes and the CellHAlign and CellVAlign attribute groups for the col and colgroup elements are omitted.

The colspan and rowspan attributes for the th and td elements allow for the creation of overlapping table areas. If an instance document contains a table with such an overlapping area, it must be rejected by the viewer component.

2.1.7 Image Module

The longdesc, height and width attributes for the img element are omitted. The content model for the img element remains unchanged.

If an instance document uses the img element to reference one or more images, then, when creating a signature, the Citizen Card Environment must select one of the following options for each image:

Note: The second variant can be selected by the Citizen Card Environment if it cannot resolve the referenced image (e.g. broken link) or if it makes no sense to display an image in this context (e.g. in the case of a Citizen Card Environment for the blind).

When a signature is verified, the Citizen Card Environment must proceed as follows for every image referenced in an instance document:

The [JPEG] image format must be supported by the viewer component of a Citizen Card Environment. However, if a [JPEG] file contains a marker of the type TEM, JPG, JPGn (n>=0), RSTn (n>=0) or APPn (n>0), then the instance document must be rejected by the Citizen Card Environment.

The [GIF] image format must also be supported by the viewer component of a Citizen Card Environment. However, if a [GIF] file contains several images (animated GIF) or an application extension, then the instance document must be rejected by the Citizen Card Environment. A [GIF] file may contain extensions of the type Comment Extension and Plain Text Extension, however the content of these extensions must not be displayed.

Other image formats may be supported by the viewer component of a Citizen Card Environment. However, the Citizen Card Environment must prevent the display of dynamic content (e.g. animated images).

2.1.8 Client-side Image Map Module

This module is not used.

2.1.9 Server-side Image Map Module

This module is not used.

2.1.10 Object Module

This module is not used.

2.1.11 Frames Module

This module is not used.

2.1.12 Target Module

This module is not used.

2.1.13 Iframe Module

This module is not used.

2.1.14 Intrinsic Events Module

This module is not used.

2.1.15 Metainformation Module

This module is not used.

2.1.16 Scripting Module

This module is not used.

2.1.17 Style Sheet Module

The title and xml:space attributes for the style element are omitted. The type attribute for the style element is prescribed and set to text/css. The media attribute for the style element is also prescribed and set to the value screen.

The content model for the style element remains unchanged.

Note: For the permitted content of the style element see section 3.

2.1.18 Style Attribute Module

This module is not used.

2.1.19 Link Module

This module is not used.

2.1.20 Base Module

This module is not used.

2.1.21 Name Identification Module

This module is not used.

2.1.22 Legacy Module

This module is not used.

2.2 XML schema for the standardised viewer format

The restrictions mentioned in the previous section are summarised and arranged as an XML schema. This XML schema should be regarded as normative and has higher priority than this description if confusion arises. The XML schema consists of a large number of individual files and can be downloaded form the following address in zipped form:

[slxhtml.schemas.zip]

The main schema file can also be downloaded from the following address:

[schema/slxhtml.xsd]

2.3 Miscellaneous

2.3.1 Comments

Comments are part of [XHTML 1.1] with a clearly defined meaning. This meaning indicates that the information in question is not intended for display. For this reason, an instance document may contain comments. The comments must not be supported by the viewer component of a Citizen Card Environment.

2.3.2 Rendering outside the canvas

Parts of an instance document that may be displayed according to [XHTML 1.1], but for which there is no mandatory rendering on the canvas, must not be displayed by the viewer component of a Citizen Card Environment. An example of this is the content of the title element ([XHTML 1.1] suggests a display in the title bar of the secure viewer window).

3 Profile of CSS 2

The profile of [CSS 2] specified in this section first defines the minimum amount of CSS2 syntax that every Citizen Card Environment must or should be able to process when displaying a document that conforms to this standardised viewer format.

In addition, every Citizen Card Environment may also process and display those parts of the CSS2 syntax not specified in this profile in the secure viewer, if this is not expressly forbidden in the sections below.

If a Citizen Card Environment is unable to interpret parts of the syntax defined as optional or recommended in this specification, then it must reject the relevant instance document.

Application developers who write instance documents that meet this standardised viewer format should only use those parts of the syntax defined in this profile as required or recommended.

3.1 Integration of CSS formats in the standardised viewer format

[CSS 2] defines a number of options for integrating CSS formats in an instance of an XHTML document. This profile limits these options to one – integration by means of the style XHTML element. All other options (definition using the XHTML attribute style, and the integration of external CSS files via the XHTML element link or via the CSS rule @import) must not be processed by a Citizen Card Environment, i.e. the relevant instance document must be rejected.

3.2 Use of CSS formats by the Citizen Card Environment

The CSS formats to be used by the viewer component of the Citizen Card Environment are defined in two stages:

The CSS formats resulting from these two steps must be taken into account by the viewer component of the Citizen Card Environment when displaying the instance document.

3.2.1 Default CSS style sheet

The default CSS style sheet that is the starting point for determining the default CSS formats to be used by the Citizen Card Environment for display in the secure viewer is a normative component in this specification and can be downloaded from the following address:

[slxhtml.default.css]

Note: It is not necessary for the viewer component of the Citizen Card Environment to be able to interpret the default style sheet. Instead it must ensure that the displayed instance document looks as if it were created by interpreting the default style sheet. To this extent there is no contradiction in the fact that CSS properties and property values are used in the default style sheet that do not necessarily need to be supported according to this specification.

3.3 At-rules

In respect of the At-rules defined in [CSS 2], the following rules apply for a Citizen Card Environment:

3.3.1 @charset

The @charset rule for specifying the character encoding of an external style sheet must not be used in an instance document because this specification only allows embedded style sheets to be used (see section 3.1) and the @charset rule must not be used in such style sheets (cf. [CSS 2], section 4.4). The viewer component of the Citizen Card Environment must reject an instance document containing a @charset rule.

3.3.2 @import

The @import rule for incorporating external CSS files must not be used in an instance document (cf. [CSS 2], section 6.3, and section 3.1 of this document). The viewer component of the Citizen Card Environment must reject an instance document containing a @import rule.

3.3.3 @media

The @media rule for specifying style sheet information for particular output media must not be used in an instance document (cf. [CSS 2], section 7). The viewer component of the Citizen Card Environment must reject an instance document containing a @media rule.

3.3.4 @page

The @page rule for defining the page properties for page-based output media may be supported by a Citizen Card Environment (cf. [CSS 2], section 13, and section 3.5.7 of this document).

3.3.5 @font-face

The @font-face rule for describing or referencing additional font families (cf. [CSS 2], section 15.3) must not be used in an instance document. The viewer component of the Citizen Card Environment must reject an instance document containing a @font-face rule.

3.4 CSS selectors

[CSS 2] defines a series of rules for setting up selectors in section 5. This section defines which of these rules a Citizen Card Environment must be able to process; these are:

The following other selectors may be supported:

3.5 CSS properties

3.5.1 Value specifications

This section defines the general requirements in relation to the value specifications to be supported for CSS properties. Unless explicitly stated otherwise for special CSS properties, they apply to all usable CSS properties.

3.5.1.1 Length specifications

A Citizen Card Environment must support a length specification in the units in, mm, cm, pc and px and should support a length specification in the relative units ex and em for a CSS property, if this is possible for this property according to [CSS 2].

3.5.1.2 Percentage values

A Citizen Card Environment must support the specification of a percentage value for a CSS property if such a specification is possible for this property according to [CSS 2].

3.5.1.3 Colours

A Citizen Card Environment must support all the options for specifying a colour listed in [CSS 2], section 4.3.6 for a CSS property, if such an option is available for this property according to [CSS 2].

The exceptions are the system colours (cf. [CSS 2], section 18.2); these must not be used in an instance document so as to prevent dependencies on the system environment. Otherwise the instance document must be rejected by the Citizen Card Environment.

3.5.1.4 Inherited and automatic values

For properties that must or should be supported by a Citizen Card Environment according to this specification, the respective property values inherit or auto should also be supported, if such values are possible for the property according to [CSS 2].

3.5.2 Spacing and borders

3.5.2.1 Margin spacing

The margin-top, margin-bottom, margin-left and margin-right properties must be supported by a Citizen Card Environment. Values specified as percentages (cf. section 3.5.1.2) should be supported.

The margin property may be supported by a Citizen Card Environment.

An instance document must not contain a negative value in the properties mentioned above. Otherwise it must be rejected by the Citizen Card Environment.

3.5.2.2 Padding spacing

The padding-top, padding-bottom, padding-left and padding-right properties must be supported by a Citizen Card Environment. Values specified as percentages (cf. section 3.5.1.2) should be supported.

The padding property may be supported by a Citizen Card Environment.

An instance document must not contain a negative value in the properties mentioned above. Otherwise it must be rejected by the Citizen Card Environment.

3.5.2.3 Borders

Border width

The border-top-width, border-bottom-width, border-left-width, border-right-width and border-width properties should be supported by a Citizen Card Environment. If the properties are supported, the predefined values thin, medium and thick should also be supported (cf. [CSS 2], section 8.5.1).

Border colour

The border-top-color, border-bottom-color, border-left-color, border-right-color and border-color properties should be supported by a Citizen Card Environment. The predefined value transparent for the border-color property may be supported (cf. [CSS 2], section 8.5.2).

Border style

The border-top-style, border-bottom-style, border-left-style, border-right-style and border-style properties should be supported by a Citizen Card Environment. If the properties are supported, the predefined values none, dashed, dotted, solid and double should also be supported; all other values may be supported (cf. [CSS 2], section 8.5.3).

Shorthand

The properties for the shorthand version of the border properties (border-top, border-bottom, border-left, border-right and border (cf. [CSS 2], section 8.5.4) should be supported by a Citizen Card Environment. The recommended values result from the three previous sections.

3.5.3 Positioning of boxes

3.5.3.1 Box type

The property for controlling the box type (display) may be supported by a Citizen Card Environment (cf. [CSS 2], section 9.2).

3.5.3.2 Positioning scheme

The property for defining the positioning scheme for a box (position, cf. [CSS 2], section 9.3) must not be contained in an instance document to prevent content from overlapping. Otherwise the instance document must be rejected by the Citizen Card Environment.

3.5.3.3 Box spacing

The property for defining the positioning scheme for a box (top, bottom, left, right; cf. [CSS 2], section 9.3) must not be contained in an instance document to prevent content from overlapping. Otherwise the instance document must be rejected by the Citizen Card Environment.

Note: It is not absolutely necessary to prohibit these properties explicitly because they are only to be used for elements that are positioned, in other words elements for which the position property is set. However, it makes no sense for these properties to appear like zombies in the instance document style sheet.

3.5.3.4 Flow around boxes

The properties for defining the flow around boxes (float, clear) may be supported by a Citizen Card Environment (cf. [CSS 2], section 9.5).

3.5.3.5 Positioning of boxes on the z-axis

The property for defining the positioning of boxes on the z-axis (z-index, cf. [CSS 2], section 9.9) must not be contained in an instance document to prevent content from overlapping. Otherwise the instance document must be rejected by the Citizen Card Environment.

Note: It is not absolutely necessary to prohibit this property explicitly because it is only to be used for elements that are positioned, in other words elements for which the position property is set. However, it makes no sense for this property to appear like a kind of zombie in the instance document style sheet.

3.5.3.6 Text direction

The properties for controlling the text direction (direction, unicode-bidi) may be supported by a Citizen Card Environment (cf. [CSS 2], section 9.10).

3.5.4 Displaying boxes

3.5.4.1 Width and height

The properties for specifying the width and height of a box (width, height, cf. [CSS 2], sections 10.2 and 10.5) must not be supported by a Citizen Card Environment to prevent content from overlapping. Otherwise the instance document must be rejected by the Citizen Card Environment.

The properties for specifying the minimum width and height of a box (min-width, min-height) may be supported by a Citizen Card Environment (cf. [CSS 2], sections 10.4 and 10.7).

The properties for specifying the maximum width and height of a box (max-width, max-height, cf. [CSS 2], sections 10.4 and 10.7) must not be supported by a Citizen Card Environment to prevent content from overlapping. Otherwise the instance document must be rejected by the Citizen Card Environment.

3.5.4.2 Line height

The properties for specifying the line height (line-height, vertical-align) should be supported by a Citizen Card (cf. [CSS 2], section 10.8). The only exception is the vertical-align property: In this case a Citizen Card Environment must be able to interpret the values sub and super.

3.5.5 Visible area in boxes

The property for specifying the visibility of a box (visibility) may be supported by a Citizen Card Environment (cf. [CSS 2], section 11).

The properties for controlling the visible area of a box (overflow, clip; cf. [CSS 2], section 11) must not be contained in an instance document to prevent hidden content. Otherwise the instance document must be rejected by the Citizen Card Environment.

3.5.6 Generated content, numbering, lists

3.5.6.1 Generated content

The property for generating content (content) may be supported by a Citizen Card Environment (cf. [CSS 2], section 12.2).

3.5.6.2 Displaying quotation marks

The property for displaying quotation marks (quotes) may be supported by a Citizen Card Environment (cf. [CSS 2], section 12.3).

3.5.6.3 Numbering

The properties for automatic numbering (counter-reset, counter-increment) may be supported by a Citizen Card Environment (cf. [CSS 2], section 12.5).

3.5.6.4 Markers and lists

Marker spacing

The property for defining the space between a marker and the associated box (marker-offset) may be supported by a Citizen Card Environment (cf. [CSS 2], section 12.6.1).

List symbols

For the property for selecting the list symbol (list-style-type) a Citizen Card Environment must support the values none, disc, circle, square, decimal, decimal-leading-zero, lower-roman, upper-roman, lower-alpha, lower-latin, upper-alpha and upper-latin. The other values may be supported (cf. [CSS 2], section 12.6.2).

Position of the list symbol

The property for positioning the list symbol in relation to the associated box (list-style-position) should be supported by a Citizen Card Environment (cf. [CSS 2], section 12.6.2).

Image as a list symbol

The property for selecting an image as a list symbol (list-style-image) may be supported by a Citizen Card Environment (cf. [CSS 2], section 12.6.2). If the Citizen Card Environment supports this property, then it must proceed in respect of the integration of the image in the signature as described in section 2.1.7.

Shorthand

The property for the shorthand version of the list properties (list-style) should be supported by a Citizen Card Environment. The recommended values result from the explanations for the list-style-type, list-style-position and list-style-image properties above (cf. [CSS 2], section 12.6.2).

3.5.7 Page-based media

The properties for page-based media may be supported by a Citizen Card Environment (size, marks, page-break-before, page-break-inside, page-break-after, page, orphans and widows (cf. [CSS 2], section 13).

3.5.8 Colours and background

3.5.8.1 Colour

The property for defining the foreground colour of the content of an element (color) must be supported by a Citizen Card Environment (cf. [CSS 2], section 14.1).

3.5.8.2 Background

The property for defining the background colour of the content of an element (background-color) must be supported by a Citizen Card Environment (cf. [CSS 2], section 14.2.1).

The properties for selecting and controlling an image as background (background-image, background-repeat, background-position, background-attachment; cf. [CSS 2], section 14.2.1) must not be contained in an instance document to prevent content from overlapping. Otherwise the instance document must be rejected by the Citizen Card Environment.

The property for the shorthand version of the background properties (background) should be supported by a Citizen Card Environment. The recommended values result from the explanations for the background-color property above (cf. [CSS 2], section 14.2.1). If the property contains values for selecting and controlling an image as background, the instance document must be rejected by the Citizen Card Environment.

3.5.9 Fonts

3.5.9.1 Font family

For the property for selecting a font family (font-family), a Citizen Card Environment must support the predefined values serif, sans-serif and monospaced for the general font families. All other values may be supported by a Citizen Card Environment (cf. [CSS 2], section 15.2.2).

If a preferred font family is specified in the instance document that cannot be displayed by the Citizen Card Environment, then the Citizen Card Environment may still display the instance document if another displayable font family has been specified as an alternative. For example, if the specification in the instance document is font-family: "Times New Roman", serif, then the Citizen Card Environment may display the instance document in the secure viewer even if it does not know the Times New Roman font family (as it must always support serif).

3.5.9.2 Font style

The properties for defining the font style (font-style) and font weight (font-weight) must be supported by a Citizen Card Environment. The values normal and italic must be supported, while the value oblique should be supported.
The property for defining the font variant (font-variant) should be supported by a Citizen Card Environment, while the property for defining the font stretch (font-stretch) may be supported by a Citizen Card Environment (cf. [CSS 2], section 15.2.3).

3.5.9.3 Font size

The property for specifying the font size (font-size) must be supported by a Citizen Card Environment. The property for specifying the stretch ratio (font-size-adjust) may be supported by a Citizen Card Environment (cf. [CSS 2], section 15.2.4).

3.5.9.4 Shorthand

The property for the shorthand version of the font properties (font) should be supported by a Citizen Card Environment (cf. [CSS 2], section 15.2.5). The recommended values result from the explanations above for the font-style, font-variant, font-weight, font-size and font-family properties and the explanations for the line-height property in section 3.5.4.2.

The additional, predefined values relating to the system fonts used (caption, icon, etc.) must not be contained in an instance document so as to prevent dependencies on the system environment. Otherwise the instance document must be rejected by the Citizen Card Environment.

3.5.10 Displaying text

3.5.10.1 Non-displayable characters

If the text of an instance document contains a character that cannot be displayed by the Citizen Card Environment, then the instance document must be rejected by the Citizen Card Environment. The character must not be represented by a placeholder.

3.5.10.2 Indent

The property for indenting the first line of a text block (text-indent) should be supported by a Citizen Card Environment (cf. [CSS 2], section 16.1).

3.5.10.3 Alignment

For the property for aligning the content of a text block (text-align) a Citizen Card Environment must support the values left, right and center. The value justified should be supported, while the specification of a string value may be supported (cf. [CSS 2], section 16.2).

3.5.10.4 Text decoration

For the property for decorating a text (text-decoration; cf. [CSS 2], section 16.3.1) a Citizen Card Environment must support the values none, underline and line-through.

The value blink must not be contained in an instance document. Otherwise the instance document must be rejected by the Citizen Card Environment.

The other values may be supported by a Citizen Card Environment.

3.5.10.5 Shadows

The property for specifying a text shadow (text-shadow) may be supported by a Citizen Card Environment (cf. [CSS 2], section 16.3.2).

3.5.10.6 Word and letter spacing

The word-spacing and letter-spacing should be supported by a Citizen Card Environment (cf. [CSS 2], section 16.4).

An instance document must not contain negative values in order to prevent content from overlapping. Otherwise the instance document must be rejected by the Citizen Card Environment.

3.5.10.7 Capitalisation

The property for specifying the capitalisation of the text of an element (text-transform) may be supported by a Citizen Card Environment (cf. [CSS 2], section 16.5).

3.5.10.8 White space

The property for the handling of white space within the text of an element (white-space) should be supported by a Citizen Card Environment (cf. [CSS 2], section 16.6).

3.5.11 Tables

3.5.11.1 Position of caption

A Citizen Card Environment should support the top and bottom properties for the property for specifying the position when labelling a table (caption-side); the properties left and right may be supported (cf. [CSS 2], section 17.4.1).

3.5.11.2 Layout algorithm

The property for defining the layout algorithm for a table (table-layout) may be supported by a Citizen Card Environment (cf. [CSS 2], section 17.5.2).

However, the fixed value must not be supported because the layout algorithm selected with it can cause content to overlap.

In general, the viewer component of the Citizen Card Environment must use a layout algorithm for a table that does not generate an overflow, in other words with which the content of every table element can be rendered so that it does not extend beyond the confines of the table element. There is an example of such an algorithm in [CSS 2], section 17.5.2, subsection Automatic table layout.

3.5.11.3 Borders

The properties for displaying borders in tables (border-collapse, border-spacing, empty-cells) may be supported by a Citizen Card Environment (cf. [CSS 2], section 17.6).

3.5.11.4 Voice output

The property for controlling the voice output of the column headers in a table (speak-header) may be supported by a Citizen Card Environment (cf. [CSS 2], section 17.7.1).

3.5.12 User interface

3.5.12.1 Cursor format

The property for controlling the cursor format (cursor; cf. [CSS 2], section 18.1) must not be contained in an instance document. Otherwise the instance document must be rejected by the Citizen Card Environment.

Note: In principle it is not necessary to prohibit this property, although it makes no sense to use it because it does not relate to the canvas. In the interests of the leanest possible specification, this property is therefore prohibited.

3.5.12.2 Contours

The properties for defining element contours (outline-width, outline-style, outline-color and outline; cf. [CSS 2], section 18.4) must not be contained in an instance document. Otherwise the instance document must be rejected by the Citizen Card Environment.

Note: In principle it is not necessary to prohibit these properties, although it makes no sense to use them because they relate to elements that are not allowed in an instance document. In the interests of the leanest possible specification, these properties are therefore prohibited.

3.5.13 Voice output

The properties for the voice output of a document (cf. [CSS 2], section 19) may be supported by a Citizen Card Environment.

4 Images in the standardised viewer format

As is apparent from sections 2 and 3, the standardised viewer format specified in this document allows images to be integrated in two different ways:

Because the images integrated in this way are not incorporated directly in the instance document, but are only referenced with a URI, the referenced image data must be included in the XML signature as additional data along with the actual instance document. The following sections specify this integration.

4.1 Integration in the XML signature

For every image referenced and to be signed in an instance document in one of the two ways mentioned above (cf. the alternatives in section 2.1.7), another dsig:Reference element must be added to the XML signature (in addition to the dsig:Reference element for the instance document). The following rules are to be obeyed:

4.1.1 Example

The following instance document is to be signed by the Citizen Card Environment:

<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Example</title>
<style type="text/css">
ul { list-style-image: url("http://example.com/list-style.gif") }
</style>
</head>
<body>
<p>
This image is also signed:
<img src="http://example.com/image.gif" alt="Example"/>
</p>
<ul>
<li>This is a bullet point represented by an image.</li>
</ul>
</body>
</html>


Here is an outline of the XML signature required for this purpose (three dots ... indicate omissions for the sake of transparency):

<?xml version="1.0" encoding="UTF-8"?>
<Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
<SignedInfo>
...
<Reference URI="http://example.com/instanceDocument.xhtml">
...
</Reference>
<Reference URI=http://example.com/image.gif"
Type="...ayer/20031031?Name=SignedImage&InstanceDocRef=0">
</Reference>
<Reference URI="http://example.com/list-style.gif"
Type="...ayer/20031031?Name=SignedImage&InstanceDocRef=0">
</Reference>
</SignedInfo>
...
</Signature>

Note: The value of the URI attribute of the first reference was chosen at random. The actual value to be used depends on the signature creation request that was sent to the Citizen Card Environment.

4.2 Process model for creating and verifying signatures

The two sections that follow describe the process model to be used by a Citizen Card Environment when processing documents that comply with the standardised viewer format defined in this document within the framework of signature creation and verification.

4.2.1 Creating a signature

4.2.2 Verifying a signature

5 References

CSS 2
Bert Bos, Håkon Wium Lie, Chris Lilley and Ian Jacobs: Cascading Style Sheets, level 2. W3C Recommendation, May 1998. Downloaded from the World Wide Web on 14 May 2004 under http://www.w3.org/TR/1998/REC-CSS2-19980512/.
GIF
Graphics Interchange Format, Version 89a. CompuServe Incorporated, July 1990. Downloaded from the World Wide Web on 14 May 2004 under http://www.w3.org/Graphics/GIF/spec-gif89a.txt.
JPEG
Eric Hamilton: JPEG File Interchange Format, Version 1.02. C-Cube Microsystems, September 1992. Downloaded from the World Wide Web on 14 May 2004 under http://www.w3.org/Graphics/JPEG/jfif3.pdf.
Keywords
S. Bradner: RFC 2119: Key words for use in RFCs to Indicate Requirement Levels. IETF Request For Comment, March 1997. Downloaded from the World Wide Web on 14 May 2004 under http://www.w3.org/Graphics/GIF/spec-gif89a.txt.
XHTML 1.1
Murray Altheim, Frank Boumphrey, Sam Dooley, Shane McCarron, Sebastian Schnitzenbaumer and Ted Wugofski: Modularization of XHTML. W3C Recommendation, April 2001. Downloaded from the World Wide Web on 14 May 2004 under http://www.w3.org/TR/2001/REC-xhtml-modularization-20010410/.
XHTML MOD
Daniel Austin, Subramanian Peruvemba, Shane McCarron, Masayasu Ishikawa: Modularization of XHTML in XML Schema. W3C Working Draft, October 2003. Downloaded from the World Wide Web on 14 May 2004 under http://www.w3.org/TR/2003/WD-xhtml-m12n-schema-20031003/.
XMLDSIG
Eastlake, Donald, Reagle, Joseph and Solo, David: XML-Signature Syntax and Processing. W3C Recommendation, February 2002. Downloaded from the World Wide Web on 14 May 2004 under http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/.

6 History

Date
Version
Changes
2005-03-01
1.2.1
  • Errata 24 and 30 eliminated.
2004-05-14
1.2.0
  • Specification converted to HTML format.
  • Version number synchronised with the other specifications for the Citizen Card model.
  • Revision of the specifications in relation to the inclusion of images in instance documents (alternative presentation of the text from the img/@lt attribute).
2003-12-18
1.0.1
  • Minor changes made to the XML schema for SLXHTML so that it can be used with commonly used XML parsers.
  • Section 2.2: Reference inserted to a main schema file for SLXHTML schemas that can be called directly.
  • Section 4.1.1: Type URIs in the examples corrected to 20031031.
2003-11-13
1.0
  • Various typographical and layout errors corrected.
  • Section 2.1.2.2: abbr and acronym elements omitted.
  • Section 2.1.6.2: span attribute for col and colgroup elements omitted.
  • Section 2.1.7: Image formats that must always be supported are specified.
  • Section 3.2.1: Note added.
  • Section 3.3.5: Use of @font-face rule set to must not.
  • Section 3.5.4.1: width, height, max-width and max-height properties set to must not to prevent overlapping.
  • Section 3.5.9.2: font-stretch property set to may.
  • Section 3.5.10.3: String value for CSS property text-align changed from should to may.
  • Section 3.5.11.1: Values left and right for the CSS property caption-side changed from should to may.
  • Section 3.5.11.2: fixed value for CSS property table-layout prohibited. Fundamental note in relation to permitted layout algorithms added.
2003-10-22
0.9
  • Definitions introduced.
  • Prohibition added in relation to the rendering of information not intended for the canvas.
  • Changes to XHTML (section 2):
    • Use of the mechanism suggested in [XHTML MOD] to create the XML schemas.
    • title attribute omitted from the Core attribute collection.
    • Attribute collection and content model for the head element restricted.
    • version attribute for the html element set to a new value.
    • cite attribute for the blockquote element omitted.
    • tt, i, b elements omitted.
    • Incorporation of the Table module completely revised.
    • longdesc, height and width attributes for the img element omitted.
    • The Metainformation module is not used.
    • title and xml:space attributes for the style element omitted.
  • Changes to CSS (section 3):
    • Section about default style sheet added.
    • Section about value specifications formatted more precisely.
    • Support for @media rule changed from may to must not.
    • Support for margin and padding properties changed from must to may.
    • Support for percentage value specifications for the properties for border and padding spacing changed from must to should.
    • Support for position, top, left, bottom and right properties changed from should to must not to prevent overlapping content.
    • Support for z-index property changed from should to must not to prevent overlapping areas.
    • clip, overflow properties: Support changed from may to must not to prevent hidden content.
    • Support for background-image, background-repeat, background-position and background-attachment properties changed from may to must not to prevent overlapping content.
    • font-family property: Support for the predefined value cursive changed from must to may.
    • font-style property: Support for the predefined value oblique changed from must to should.
    • font property: Predefined values relating to the system fonts used (caption, icon, etc.) changed from may to must not so as to prevent dependencies on the system environment.
    • text-decoration property: Predefined value blink changed from may to must not.
    • word-spacing, letter-spacing properties: Negative values excluded to prevent overlapping content.
    • cursor, outline-width, outline-style, outline-color and outline properties: Changed from may to must not because the properties cannot be applied to the canvas (cursor) or relate to elements that must not be contained in the instance document (all others).
2003-08-25
0.4
  • Attribute collection I18N in XHTML profile omitted.
  • Section 2.3.1 relating to comments in the instance document inserted.
  • Section 3.2 relating to At-rules inserted.
  • Section 3.3 relating to CSS selectors revised.
  • Section 3.4 relating to CSS properties revised.
  • Section 4 relating to the signing of instance documents containing images inserted.
2003-07-17
0.3
  • Created