W3C

Content Selection Primer 1.0

W3C Working Draft 10 October 2006

This version:
http://www.w3.org/TR/2006/WD-cselection-primer-20061010/
Latest version:
http://www.w3.org/TR/cselection-primer/
Previous version:
This is the First Public Working Draft
Editors:
Rhys Lewis, Volantis Systems Ltd. <rhys@volantis.com>
Roland Merrick, IBM <roland_merrick@uk.ibm.com>

Abstract

Content Selection for Device Independence [DISelect] is a specification that allows authors to choose between different versions of content for use in different circumstances. This Primer is designed to provide the reader with the basic knowledge required to make effective use of this markup. It positions DISelect in relation to other methods of content selection. It also describes the features of DISelect and illustrates how they can be used in a variety of scenarios using a number of examples.

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 is the First Public Working Draft of a possible future W3C Recommendation.

This is a W3C Working Draft of the Content Selection Primer, for review by W3C members and other interested parties. Please send review comments to public-diselect-editors@w3.org. This list is archived at http://lists.w3.org/Archives/Public/public-diselect-editors/.

This draft is an outline. It shows the structure of the document. It is being published to satisfy references from other specifications that are being published at the same time. DIWG expects to update this draft shortly.

Publication as a 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 is published as part of the W3C Device Independence Activityby the Device Independence Working Group (Member Only Link). It is a deliverable as defined in the Charter of that group.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. This document is informative only. 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.

Table of Contents

1 Introduction
    1.1 Structure of the specifications
    1.2 Separation of concerns
    1.3 Adaptation
        1.3.1 Selection
        1.3.2 Transformation
2 Current capabilities for content selection
    2.1 CSS
        2.1.1 CSS Media types
        2.1.2 Display property to hide inappropriate content
        2.1.3 Examples and diagrams?
        2.1.4 Weaknesses
    2.2 Content Negotiation
        2.2.1 Representations and resources
        2.2.2 Media types, natural language
        2.2.3 HTTP content negotiation
        2.2.4 Examples and diagrams c.f. DCO
        2.2.5 Weaknesses
    2.3 XHTML 2
    2.4 SMIL
3 Enriched capabilities with DISelect
    3.1 Richer set of alternatives
        3.1.1 Wider variety of complete resource representations
        3.1.2 Fragments within a resource representation
    3.2 Richer set of criteria for selection
        3.2.1 Anything in the delivery context
            3.2.1.1 Device characteristics
            3.2.1.2 User preferences
            3.2.1.3 Context of the request
        3.2.2 Criteria outside the DC
            3.2.2.1 Metadata associated with the document
            3.2.2.2 Document itself
            3.2.2.3 Context of the processing of the request
    3.3 Content selection models
        3.3.1 In-line selection
            3.3.1.1 No separate fetch. Material already in line
            3.3.1.2 Weakest separation of concerns
            3.3.1.3 Selection occurs within the scope of the request for the referring resource
        3.3.2 In-line selection with inclusion
            3.3.2.1 Fetch by embed
            3.3.2.2 Supports separation of concerns
            3.3.2.3 Selection occurs within scope of request for the referring resource
        3.3.3 Separate selection
            3.3.3.1 Strongest separation of concerns
            3.3.3.2 Highest diversity of representation
            3.3.3.3 By reference
            3.3.3.4 Separate fetch from UA
            3.3.3.5 Content negotiation independent of that for the referring resource

Appendices

A References
    A.1 Informative References
B Changelog (Non-Normative)
    B.1 Changes in this Version
C Acknowledgements (Non-Normative)


1 Introduction

Processes, 'in the large', the overall picture into which DISelect fits.

1.1 Structure of the specifications

. . .

1.2 Separation of concerns

. . .

1.3 Adaptation

1.3.1 Selection

. . .

1.3.2 Transformation

. . .

2 Current capabilities for content selection

There is material in DCO that we should reference

2.1 CSS

2.1.1 CSS Media types

. . .

2.1.2 Display property to hide inappropriate content

. . .

2.1.3 Examples and diagrams?

. . .

2.1.4 Weaknesses

All content gets sent to the client and processed there.

Limitation in criteria for selection

Proliferation of style sheets because of lack of composition capabilities

Even the new media queries is too rigid because the characteristics are named in the language

. . .

2.2 Content Negotiation

2.2.1 Representations and resources

Existing HTTP mechanisms

. . .

2.2.2 Media types, natural language

. . .

2.2.3 HTTP content negotiation

. . .

2.2.4 Examples and diagrams c.f. DCO

. . .

2.2.5 Weaknesses

Can't support multiple representations of the same content type and language but different size, color, .....

Can't resolve situations when there is no available representation and the only resolution would be to create a suitable version by transcoding

. . .

2.3 XHTML 2

Embedding attributes src and body content

2.4 SMIL

. . .

3 Enriched capabilities with DISelect

Tell it as a story. Here is what we can do today. But what if... two gifs of different sizes? Content negotiation can't cope....

3.1 Richer set of alternatives

3.1.1 Wider variety of complete resource representations

Multiple alternatives for a single media type.

3.1.2 Fragments within a resource representation

DISelect in-line within a single document, for example.

3.2 Richer set of criteria for selection

Much more than just media type or language

3.2.1 Anything in the delivery context

3.2.1.1 Device characteristics
3.2.1.2 User preferences
3.2.1.3 Context of the request

HTTP headers

Parameters

3.2.2 Criteria outside the DC

These are not supported at all by CSS or by content selection HTTP style

. . .

3.2.2.1 Metadata associated with the document

Enriched semantics - cf metadata workshop

3.2.2.2 Document itself
3.2.2.3 Context of the processing of the request

3.3 Content selection models

3.3.1 In-line selection

3.3.1.1 No separate fetch. Material already in line
3.3.1.2 Weakest separation of concerns
3.3.1.3 Selection occurs within the scope of the request for the referring resource

. . .

3.3.2 In-line selection with inclusion

3.3.2.1 Fetch by embed

XInclude style model

3.3.2.2 Supports separation of concerns
3.3.2.3 Selection occurs within scope of request for the referring resource

. . .

3.3.3 Separate selection

Enhanced 'maps' (c.f. apache web server)

Enhanced ways of selecting between different versions of a resource

3.3.3.1 Strongest separation of concerns
3.3.3.2 Highest diversity of representation
3.3.3.3 By reference

. . .

3.3.3.4 Separate fetch from UA
3.3.3.5 Content negotiation independent of that for the referring resource

src attribute in XHTML 2 or img style fetch

. . .

A References

A.1 Informative References

DISelect
Content Selection for Device Independence (DISelect) 1.0 R. Lewis and R. Merrick 2006 (See http://www.w3.org/TR/cselection)
Glossary
Glossary of Terms for Device Independence R. Lewis, 2005 (See http://www.w3.org/TR/di-gloss/.)
Authoring Challenges
Authoring Challenges for Device Independence R. Lewis, 2003. W3C Note (See http://www.w3.org/TR/acdi/.)
DI Principles
Device Independence Principles R. Gimson, 2003. W3C Note (See http://www.w3.org/TR/di-princ/.)
XHTML 2
XHTMLTM 2 J. Axelsson et al., 2003 W3C Working Draft (See http://www.w3.org/TR/xhtml2/.)
XForms
XForms 1.0 M. Dubinko et al., 2003 W3C Recommendation (See http://www.w3.org/TR/xforms/.)
CSS
Cascading Style Sheets, level 2B. Boss et al., 2004 W3C Recommendation (See http://www.w3.org/TR/CSS2/.)
RDF Primer
RDF Primer F. Manola et al., 2004 W3C Recommendation (See http://www.w3.org/TR/rdf-primer/.)
ECMAScript
ECMAScript Language Specification ECMA (European Computer Manufacturers Association) (See http://www.ecma-international.org/publications/standards/Ecma-262.htm.)
XSLT
XSL Transformations (XSLT) Version 1.0 J. Clark, 1999 W3C Recommendation (See http://www.w3.org/TR/xslt.)

B Changelog (Non-Normative)

B.1 Changes in this Version

  • .

C Acknowledgements (Non-Normative)

At the time of publication, the participants of the Device Independence Working Group are:

The Device Independence Working Group has benefited in its work from the participation and contributions of a number of people not currently members of the Working Group, including in particular those named below. Affiliations given are those current at the time of their work with the WG.