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<h1>Glossary of Terms for Device Independence</h1>

<h2>W3C Working Draft 18 January 2005</h2>
<dl>
  <dt>This version:</dt>
    <dd><a href="http://www.w3.org/TR/2005/WD-di-gloss-20050118/">http://www.w3.org/TR/2005/WD-di-gloss-20050118/</a></dd>
  <dt>Latest version:</dt>
    <dd><a
      href="http://www.w3.org/TR/di-gloss/">http://www.w3.org/TR/di-gloss/</a></dd>
  <dt>Previous version:</dt>
    <dd><a
      href="http://www.w3.org/TR/2003/WD-di-gloss-20030825/">http://www.w3.org/TR/2003/WD-di-gloss-20030825/</a></dd>
  <dt>Author:</dt>
    <dd>Rhys Lewis (Volantis Systems) <a
      href="mailto:rhys.lewis@volantis.com">&lt;rhys.lewis@volantis.com&gt;</a></dd>
  <dt>Contributors:</dt>
    <dd>See <a href="#sec-acknowledgements">D Acknowledgements</a></dd>
</dl>

<p class="copyright"><a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a>
&#xa9;2003-2005 <a href="http://www.w3.org/"><abbr
title="World Wide Web Consortium">W3C</abbr></a> <sup>&#xae;</sup> ( <a
href="http://www.csail.mit.edu/"><abbr
title="Massachusetts Institute of Technology">MIT</abbr></a> , <a
href="http://www.ercim.org/"><abbr
title="European Research Consortium for Informatics and Mathematics ">ERCIM</abbr></a>
, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a
href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>,
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use</a> rules apply.</p>
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<h2><a name="abstract" id="abstract">Abstract</a></h2>

<p>This document is a glossary of terms used in other documents produced by
the Device Independence Working Group (DIWG). Details of the entire series of
documents can be found on the <a href="http://www.w3.org/2001/di/">W3C Device
Independence Activity</a> home page.</p>

<h2><a name="status" id="status">Status of this Document</a></h2>

<p><em>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 <a href="http://www.w3.org/TR/">W3C technical reports index</a>
at http://www.w3.org/TR/.</em></p>

<p>This glossary is published and maintained by <a href="http://www.w3.org/2001/di/Group/">DIWG</a>(member only link), part of the <a
href="http://www.w3.org/2001/di/">W3C Device Independence Activity</a>. The
DIWG activity statement can be seen at <a
href="http://www.w3.org/2001/di/Activity">http://www.w3.org/2001/di/Activity</a>.</p>
<p>The glossary is maintained as a Working Draft of a future W3C Note. This
allows it to be revised at appropriate intervals. Updates take place in
support of new work being carried out by the DIWG. In general, it is
inappropriate to use W3C Working Drafts as formal reference material or to
cite them as other than "work in progress". Because this document is subject
to change, other authors wishing to cite definitions in this glossary should
exercise caution. Updates to the glossary are made in such a way as to avoid
invalidating references, as long as those references conform to the
mechanisms described in the section <a
href="#sec-using-and-maintaining">Using and Maintaining the Glossary</a>.
However, in support of its work, DIWG may need to modify definitions in newer
versions of this document.</p>

<p>A list of current public W3C Working Drafts can be found at <a
href="http://www.w3.org/TR/">http://www.w3.org/TR</a>.</p>

<p>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.</p>

<p>Comments on this document can be sent to <a
href="mailto:www-di@w3.org">www-di@w3.org</a>, the public forum for
discussion of the W3C's work on Device Independence. To subscribe, send an
email to <a href="mailto:www-di-request@w3.org">www-di-request@w3.org</a>
with the word subscribe in the subject line (include the word unsubscribe if
you want to unsubscribe). The <a
href="http://lists.w3.org/Archives/Public/www-di/">archive</a> for the list
is accessible online.</p>

<p>Information on how to use this document and how it is maintained can be
found in <a href="#sec-using-and-maintaining">Using and Maintaining the
Glossary</a>.</p>


<h2><a name="contents" id="contents">Table of Contents</a></h2>
<ul class="contents">
  <li><a href="#sec-changes">Changes to the Glossary</a>
    <ul class="contents">
      <li><a href="#sec-changes-2003-08-25">Changes from the Version
        Published on 25 August 2003</a></li>
    </ul>
  </li>
  <li><a href="#sec-glossary">Glossary</a></li>
  <li><a href="#sec-using-and-maintaining">A Using and Maintaining the
    Glossary</a>
    <ul class="contents">
      <li><a href="#sec-using">A.1 Using the Glossary</a></li>
      <li><a href="#sec-maintaining">A.2 Maintaining the Glossary</a></li>
    </ul>
  </li>
  <li><a href="#sec-previous-versions">B Previous Versions of Definitions</a>
    <ul class="contents">
      <li><a href="#sec-updated">B.1 Definitions that Have Been
      Updated</a></li>
      <li><a href="#sec-removed">B.2 Definitions that Have Been
      Removed</a></li>
      <li><a href="#sec-deprecated">B.3 Definitions that Have Been
        Deprecated</a></li>
    </ul>
  </li>
  <li><a href="#sec-references">C References</a></li>
  <li><a href="#sec-acknowledgements">D Acknowledgements</a></li>
</ul>

<h3><a name="issues" id="issues">Verbatim Definitions</a></h3>

<p>Terms whose definitions are taken directly from other sources are marked
as follows:</p>
<dl>
  <dt>Term taken verbatim from another source</dt>
    <dd class="verbatim">Definition taken from another source</dd>
</dl>
<hr />

<h2><a name="sec-changes" id="sec-changes">Changes to the Glossary</a></h2>

<h3><a name="sec-changes-2003-08-25" id="sec-changes-2003-08-25">Changes from
the Version Published on 25 August 2003</a></h3>
<ul>
  <li>The definition of the term <a
    href="#def-decomposition-v2">decomposition</a> has been modified. The <a
    href="#def-decomposition">previous version</a> of the definition remains
    available for reference.</li>
  <li>A new definition for the term <a
    href="#def-aggregation">aggregation</a> has been added</li>
  <li>A new definition for the term <a
    href="#def-aggregated-authored-unit">aggregated authored unit</a> has
    been added</li>
  <li>A definition for the term <a href="#def-physical-transducer">Physical
    Transducer</a> has been added.</li>
  <li>A new definition for <a href="#def-single-authoring">Single
    Authoring</a> has been added.</li>
  <li>A new definition for <a href="#def-multiple-authoring">Multiple
    Authoring</a> has been added.</li>
  <li>A new definition for <a href="#def-flexible-authoring">Flexible
    Authoring</a> has been added.</li>
  <li>The definition of <a href="#def-delivery-context-v2">Delivery
    Context</a> has been updated. The <a
    href="#def-delivery-context">previous version</a> of the definition
    remains available for reference.</li>
</ul>

<h2><a name="sec-glossary" id="sec-glossary">Glossary</a></h2>
<dl>
  <dt><a name="def-access-mechanism" id="def-access-mechanism">Access
  Mechanism</a></dt>
    <dd>A combination of hardware (including one or more <a
      href="#def-device">devices</a> and network connections) and software
      (including one or more <a href="#def-user-agent">user agents</a>) that
      allows a <a href="#def-user">user</a> to perceive and <a
      href="#def-interaction">interact</a> with the Web using one or more <a
      href="#def-modality">modalities</a>. (sight, sound, keyboard, voice
      etc.)</dd>
  <dt><a name="def-active-perceivable-unit"
  id="def-active-perceivable-unit">Active Perceivable Unit</a></dt>
    <dd>A <a href="#def-perceivable-unit">perceivable unit</a> that is
      currently being rendered by the <a href="#def-user-agent">user
      agent</a> and with which <a href="#def-interaction">interaction</a> may
      be possible.</dd>
  <dt><a name="def-adaptation" id="def-adaptation">Adaptation</a></dt>
    <dd>a process of selection, generation or modification that produces one
      or more <a href="#def-perceivable-unit">perceivable units</a> in
      response to a requested <a
      href="#def-uniform-resource-identifier">uniform resource identifier</a>
      in a given delivery context.</dd>
  <dt><a name="def-adaptation-preferences"
  id="def-adaptation-preferences">Adaptation Preferences</a></dt>
    <dd>A set of preferences, specified by a <a href="#def-user">user</a>,
      that may affect the <a href="#def-adaptation">adaptation</a> for a
      given delivery context, and so change the resultant <a
      href="#def-user-experience">user experience</a>.</dd>
  <dt><a name="def-application-personalization"
  id="def-application-personalization">Application Personalization</a></dt>
    <dd>A set of factors, specified by a <a href="#def-user">user</a> or
      other aspects of the <a href="#def-delivery-context-v2">delivery
      context</a>, that may affect the functionality of an application,
      independently of its <a href="#def-adaptation">adaptation</a> and
      delivery, and so change the resultant <a
      href="#def-user-experience">user experience</a>."</dd>
  <dt id="def-aggregation">Aggregation</dt>
    <dd>The act of combining materials in various ways.</dd>
    <dd>Where the materials being aggregated are <a
      href="#def-authored-unit">authored units</a>, the result of aggregation
      is an <a href="#def-aggregated-authored-unit">aggregated authored
      unit</a>.</dd>
  <dt id="def-aggregated-authored-unit">Aggregated Authored Units</dt>
    <dd>A set of <a href="#def-authored-unit">authored units</a> that have
      been <a href="#def-aggregation">aggregated</a> in some way.</dd>
  <dt><a name="def-authored-unit" id="def-authored-unit">Authored
  Unit</a></dt>
    <dd>Some set of material created as a single entity by an author.
      Examples include a collection of markup, a style sheet, and a media <a
      href="#def-resource">resource</a>, such as an image or audio clip.</dd>
  <dt><a name="def-browser" id="def-browser">Browser</a></dt>
    <dd>A <a href="#def-user-agent">user agent</a> that allows a <a
      href="#def-user">user</a> to perceive and <a
      href="#def-interaction">interact</a> with information on the Web.</dd>
    <dd>This definition was developed from that in <a
      href="#weaving-web">Weaving the Web: Glossary</a>.</dd>
  <dt><a name="def-client" id="def-client">Client</a></dt>
    <dd class="verbatim">The role adopted by an application when it is
      retrieving and/or rendering <a href="#def-resource">resources</a> or <a
      href="#def-resource-manifestation">resource manifestations</a>.</dd>
    <dd>This term was taken verbatim from <a href="#ref-wca-terms">Web
      Characterization Terminology &amp; Definitions Sheet</a>.</dd>
  <dt><a name="def-content-negotiation" id="def-content-negotiation">Content
  Negotiation</a></dt>
    <dd class="verbatim">The mechanism for selecting the appropriate <a
      href="#def-http-representation">HTTP representation</a> when servicing
      a <a href="#def-request">request</a>. The <a
      href="#def-http-representation">HTTP representation</a> of entities in
      any response can be negotiated (including error responses).</dd>
    <dd>This term was developed from that in <a href="#ref-http">Hypertext
      Transfer Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-decomposition-v2"
  id="def-decomposition-v2">Decomposition</a></dt>
    <dd>The act of dividing up one or more <a
      href="#def-authored-unit">authored units</a>, or an <a
      href="#def-aggregated-authored-unit">aggregated authored unit</a>,
      during creation of a set of <a href="#def-perceivable-unit">perceivable
      units</a> appropriate for a particular delivery context.</dd>
  <dt><a name="def-delivery-context-v2" id="def-delivery-context-v2">Delivery
  Context</a></dt>
    <dd class="">A set of attributes that characterizes the capabilities of
      the <a href="#def-access-mechanism">access mechanism</a>, the
      preferences of the <a href="#def-user">user</a> and other aspects of
      the context into which a web page is to be delivered.</dd>
  <dt><a name="def-delivery-unit" id="def-delivery-unit">Delivery
  Unit</a></dt>
    <dd>A set of material transferred between two cooperating web programs as
      the response to a single <a href="#def-http-request">HTTP request</a>.
      The transfer might, for example, be between an <a
      href="#def-origin-server">origin server</a> and a <a
      href="#def-user-agent">user agent</a>.</dd>
    <dd>Users are not normally aware of individual delivery units.</dd>
  <dt><a name="def-device" id="def-device">Device</a></dt>
    <dd>An apparatus through which a <a href="#def-user">user</a> can
      perceive and <a href="#def-interaction">interact</a> with the Web</dd>
  <dt><a name="def-flexible-authoring" id="def-flexible-authoring">Flexible
  Authoring</a></dt>
    <dd class="">An authoring style in which an appropriate set of <a
      href="#def-variant">variants</a> of each <a
      href="#def-resource">resource</a> is created for use in the <a
      href="#def-user-experience">user experience</a> for each <a
      href="#def-delivery-context-v2">delivery context</a>.</dd>
    <dd class="">Flexible authoring lies within a spectrum of authoring
      styles bounded at one end by <a href="#def-single-authoring">single
      authoring</a> and at the other by <a
      href="#def-multiple-authoring">multiple authoring</a>.</dd>
  <dt><a name="def-focus-of-attention" id="def-focus-of-attention">Focus of
  Attention</a></dt>
    <dd>The point in an <a href="#def-active-perceivable-unit">active
      perceivable unit</a> on which the user's attention is currently
    focused.</dd>
    <dd>For example, this might be a paragraph of text or an image on which
      the user is concentrating.</dd>
  <dt><a name="def-functional-adaptation"
  id="def-functional-adaptation">Functional Adaptation</a></dt>
    <dd>An <a href="#def-adaptation">adaptation</a> that generates a <a
      href="#def-functional-user-experience">functional user experience</a>
      from a particular <a href="#def-resource">resource</a>.</dd>
  <dt><a name="def-functional-user-experience"
  id="def-functional-user-experience">Functional User Experience</a></dt>
    <dd>A set of one or more <a href="#def-perceivable-unit">perceivable
      units</a> that enables a <a href="#def-user">user</a> to complete the
      function intended by the author for a given <a
      href="#def-resource">resource</a> via a given <a
      href="#def-access-mechanism">access mechanism</a>.</dd>
  <dt><a name="def-gateway" id="def-gateway">Gateway</a></dt>
    <dd class="verbatim">A gateway is an intermediary which acts as a <a
      href="#def-server">server</a> on behalf of some other <a
      href="#def-server">server</a> with the purpose of supplying <a
      href="#def-resource">resources</a> or <a
      href="#def-resource-manifestation">resource manifestations</a> from
      that other <a href="#def-server">server</a>. <a
      href="#def-client">Clients</a> using a gateway know the gateway is
      present but do not know that it is an intermediary.</dd>
    <dd>This term was taken verbatim from <a href="#ref-wca-terms">Web
      Characterization Terminology &amp; Definitions Sheet</a>.</dd>
  <dt><a name="harmonized-adaptation" id="harmonized-adaptation">Harmonized
  Adaptation</a></dt>
    <dd>A <a href="#def-functional-adaptation">functional adaptation</a>
      sufficiently harmonized with the <a
      href="#def-delivery-context-v2">delivery context</a> that it generates
      a <a href="#def-harmonized-user-experience">harmonized user
      experience</a>.</dd>
  <dt><a name="def-harmonized-user-experience"
  id="def-harmonized-user-experience">Harmonized User Experience</a></dt>
    <dd>A <a href="#def-functional-user-experience">functional user
      experience</a> that is sufficiently harmonized with the <a
      href="#def-delivery-context-v2">delivery context</a> to meet the
      quality criteria of the author.</dd>
  <dt><a name="def-http-client" id="def-http-client">HTTP Client</a></dt>
    <dd>A program that establishes connections for the purpose of sending <a
      href="#def-http-request">HTTP requests</a>.</dd>
    <dd>This term was developed from the definition of
      <strong>client</strong> in <a href="#ref-http">Hypertext Transfer
      Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-http-gateway" id="def-http-gateway">HTTP Gateway</a></dt>
    <dd>An <a href="#def-http-server">HTTP server</a> which acts as an
      intermediary for some other <a href="#def-http-server">HTTP server</a>.
      Unlike an <a href="#def-http-proxy">HTTP proxy</a>, an HTTP gateway
      receives requests as if it were the <a href="#def-origin-server">origin
      server</a> for the requested <a href="#def-resource">resource</a>; the
      requesting <a href="#def-http-client">HTTP client</a> may not be aware
      that it is communicating with an HTTP gateway.</dd>
    <dd>This term was developed from the definition of
      <strong>gateway</strong> in <a href="#ref-http">Hypertext Transfer
      Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-http-payload-entity" id="def-http-payload-entity">HTTP
  Payload Entity</a></dt>
    <dd>The information transferred as the payload of an <a
      href="#def-http-request">HTTP request</a> or <a
      href="#def-http-response">HTTP response</a>.</dd>
    <dd>An HTTP payload entity consists of meta-information in the form of
      entity-header fields and content in the form of an entity-body.</dd>
    <dd>This term was developed from the definition of
      <strong>entity</strong> in <a href="#ref-http">Hypertext Transfer
      Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-http-proxy" id="def-http-proxy">HTTP Proxy</a></dt>
    <dd>An intermediary program which acts as both an <a
      href="#def-http-server">HTTP server</a> and as an <a
      href="#def-http-client">HTTP client</a> for the purpose of making
      requests on behalf of other <a href="#def-http-client">HTTP
    clients</a>.</dd>
    <dd><a href="#def-http-request">HTTP requests</a> are serviced internally
      or by passing them on, with possible translation, to other <a
      href="#def-http-server">HTTP servers</a>. An HTTP proxy must implement
      both the client and server requirements of this specification. A
      "transparent proxy" is a proxy that does not modify the <a
      href="#def-http-request">HTTP request</a> or the <a
      href="#def-http-response">HTTP response</a> beyond what is required for
      proxy authentication and identification. A "non-transparent proxy" is a
      proxy that modifies the <a href="#def-http-request">HTTP request</a> or
      <a href="#def-http-response">HTTP response</a> in order to provide some
      added service to the <a href="#def-user-agent">user agent</a>, such as
      group annotation services, media type transformation, protocol
      reduction, or anonymity filtering. Except where either transparent or
      non-transparent behavior is explicitly stated, the HTTP proxy
      requirements apply to both types of proxies.</dd>
    <dd>This term was developed from the definition of <strong>proxy</strong>
      in <a href="#ref-http">Hypertext Transfer Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-http-representation" id="def-http-representation">HTTP
  Representation</a></dt>
    <dd>An <a href="#def-http-payload-entity">HTTP payload entity</a>,
      included in an <a href="#def-http-response">HTTP response</a>, that is
      subject to <a href="#def-content-negotiation">content negotiation</a>.
      There may exist multiple representations associated with a particular
      <a href="#def-http-response">HTTP response</a> status.</dd>
    <dd>This term was developed from the definition for
      <strong>representation</strong> in <a href="#ref-http">Hypertext
      Transfer Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-http-request" id="def-http-request">HTTP Request</a></dt>
    <dd>An HTTP message sent by an <a href="#def-http-client">HTTP client</a>
      requesting that some operation be performed on some <a
      href="#def-resource">resource</a>. Also, the act of sending such a
      message is termed <strong>making a request</strong>.</dd>
    <dd>This term was developed from the definition of
      <strong>request</strong> in <a href="#ref-http">Hypertext Transfer
      Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-http-response" id="def-http-response">HTTP
  Response</a></dt>
    <dd>An HTTP message sent back to an <a href="#def-http-client">HTTP
      client</a> in response to a previous <a href="#def-http-request">HTTP
      request</a>.</dd>
    <dd>This term was developed from the definition of
      <strong>response</strong> in <a href="#ref-http">Hypertext Transfer
      Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-http-server" id="def-http-server">HTTP Server</a></dt>
    <dd>An application program that accepts connections in order to service
      <a href="#def-http-request">HTTP requests</a> by sending back <a
      href="#def-http-request">HTTP responses</a>.</dd>
    <dd>Any given program may be capable of being both an <a
      href="#def-http-client">HTTP client</a> and an HTTP server; our use of
      these terms refers only to the role being performed by the program for
      a particular connection, rather than to the program's capabilities in
      general. Likewise, any <a href="#def-http-server">HTTP server</a> may
      act as an <a href="#def-origin-server">origin server</a>, <a
      href="#def-http-proxy">HTTP proxy</a>, <a href="#def-http-gateway">HTTP
      gateway</a>, or tunnel, switching behavior based on the nature of each
      request.</dd>
    <dd>This term was developed from the definition of
      <strong>server</strong> in <a href="#ref-http">Hypertext Transfer
      Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-interaction" id="def-interaction">Interaction</a></dt>
    <dd>An activity by which a user can influence the data and processing of
      an application by modifying the information associated with an <a
      href="#def-active-perceivable-unit">active perceivable unit</a>.</dd>
    <dd>A common form of this kind of activity is the entry of data into an
      <a href="#def-active-perceivable-unit">active perceivable unit</a> that
      contains a form.</dd>
  <dt><a name="def-modality" id="def-modality">Modality</a></dt>
    <dd>The type of communication channel used for <a
      href="#def-interaction">interaction</a> . This might be, for example,
      visual, gestural or based on speech. It also covers the way an idea is
      expressed or perceived, or the manner in which an action is performed.
      This definition is based on unpublished work of the Multimodal
      Interaction group.</dd>
  <dt><a name="def-multiple-authoring" id="def-multiple-authoring">Multiple
  Authoring</a></dt>
    <dd class="">An authoring style in which a different <a
      href="#def-variant">variant</a> of each <a
      href="#def-resource">resource</a> is created for use in the <a
      href="#def-user-experience">user experience</a> for each <a
      href="#def-delivery-context-v2">delivery context</a> without <a
      href="#def-adaptation">adaptation</a>.</dd>
    <dd class="">Multiple authoring represents one end of a spectrum of
      authoring styles that include <a href="#def-single-authoring">single
      authoring</a> and <a href="#def-flexible-authoring">flexible
      authoring</a>. It represents a theoretical extreme that is rarely
      achieved in practice. Though it offers authors complete control over
      the user experience on each device, the associated development and
      maintenance costs are usually considered prohibitive.</dd>
  <dt><a name="def-navigation" id="def-navigation">Navigation</a></dt>
    <dd>An activity, based on a mechanism provided by an <a
      href="#def-active-perceivable-unit">active perceivable unit</a>, by
      which a user can alter their <a href="#def-focus-of-attention">focus of
      attention</a>. If the new <a href="#def-focus-of-attention">focus of
      attention</a> is in a different <a
      href="#def-perceivable-unit">perceivable unit</a>, that unit becomes an
      <a href="#def-active-perceivable-unit">active perceivable unit</a>.</dd>
    <dd>One common form of this kind of mechanism is the link, a region
      within an <a href="#def-active-perceivable-unit">active perceivable
      unit</a> which can be activated by a suitable user action.</dd>
  <dt><a name="def-origin-server" id="def-origin-server">Origin
  Server</a></dt>
    <dd class="verbatim">The <a href="#def-server">server</a> on which a
      given resource resides or is to be created.</dd>
    <dd>This term was taken verbatim from <a href="#ref-http">Hypertext
      Transfer Protocol -- HTTP/1.1</a>.</dd>
  <dt class=""><a name="def-physical-transducer"
  id="def-physical-transducer">Physical Transducer</a></dt>
    <dd class="">An entity by which a <a href="#def-user">user</a> interacts
      physically with a <a href="#def-device">device</a>.</dd>
  <dt><a name="def-perceivable-unit" id="def-perceivable-unit">Perceivable
  Unit</a></dt>
    <dd>A set of material which, when <a href="#def-rendering">rendered</a>
      by a <a href="#def-user-agent">user agent</a>, may be perceived by a <a
      href="#def-user">user</a> and with which <a
      href="#def-interaction">interaction</a> may be possible.</dd>
    <dd><a href="#def-user-agent">User agents</a> may choose to render some
      or all of the material they receive in a <a
      href="#def-delivery-unit">delivery unit</a> as a single perceivable
      unit or as multiple perceivable units.</dd>
    <dd>Most perceivable units provide both presentation and the means for <a
      href="#def-interaction">interaction</a>. However, on some types of
      device, such as printers, perceivable units might contain only
      presentation.</dd>
  <dt><a name="def-proxy" id="def-proxy">Proxy</a></dt>
    <dd class="verbatim">A proxy is an intermediary which acts as both a <a
      href="#def-server">server</a> and a <a href="#def-client">client</a>
      for the purpose of retrieving <a href="#def-resource">resources</a> or
      <a href="#def-resource">resource manifestations</a> on behalf of other
      <a href="#def-client">clients</a>. <a href="#def-client">Clients</a>
      using a proxy know the proxy is present and that it is an
    intermediary.</dd>
    <dd>This term was taken verbatim from <a href="#ref-wca-terms">Web
      Characterization Terminology &amp; Definitions Sheet</a>.</dd>
  <dt><a name="def-rendering" id="def-rendering">Rendering</a></dt>
    <dd>The act of converting <a href="#def-perceivable-unit">perceivable
      units</a> into physical effects that can be perceivable by a <a
      href="#def-user">user</a> and with which a <a href="#def-user">user</a>
      may be able to <a href="#def-interaction">interact</a>.</dd>
  <dt><a name="def-rendering-preferences"
  id="def-rendering-preferences">Rendering Preferences</a></dt>
    <dd>A set of preferences, specified by a <a href="#def-user">user</a>,
      that may affect the way the user agent renders a perceivable unit, and
      so change the resultant user experience.</dd>
  <dt><a name="def-request" id="def-request">Request</a></dt>
    <dd class="verbatim">A message describing an atomic operation to be
      carried out in the context of a specified <a
      href="#def-resource">resource</a>.</dd>
    <dd>This term was taken verbatim from <a href="#ref-wca-terms">Web
      Characterization Terminology &amp; Definitions Sheet</a>.</dd>
  <dt><a name="def-resource" id="def-resource">Resource</a></dt>
    <dd class="verbatim">A network data object or service that can be
      identified by a <a href="#def-uniform-resource-identifier">URI</a>.
      Resources may be available in multiple representations (e.g. multiple
      languages, data formats, size, resolutions) or vary in other ways.</dd>
    <dd>This term was taken verbatim from <a href="#ref-http">Hypertext
      Transfer Protocol -- HTTP/1.1</a></dd>
  <dt><a name="def-resource-manifestation"
  id="def-resource-manifestation">Resource Manifestation</a></dt>
    <dd class="verbatim">One specific rendition of a <a
      href="#def-resource">resource</a> at a specific point in time and
    space.</dd>
    <dd class="verbatim">A conceptual mapping exists between a <a
      href="#def-resource">resource</a> and a resource manifestation (or set
      of manifestations), in the sense that the resource has certain
      properties - e.g., its <a
      href="#def-uniform-resource-identifier">URI</a>, its intended purpose,
      etc. - which are inherited by each manifestation, although the specific
      structure, form, and content of the manifestation may vary according to
      factors such as the environment in which it is displayed, the time it
      is accessed, etc. Regardless of the form the manifestation's rendering
      ultimately takes, the conceptual mapping to the <a
      href="#def-resource">resource</a> is preserved.</dd>
    <dd>This term was taken verbatim from <a href="#ref-wca-terms">Web
      Characterization Terminology &amp; Definitions Sheet</a></dd>
  <dt><a name="def-response" id="def-response">Response</a></dt>
    <dd class="verbatim">A message containing the result of an executed <a
      href="#def-request">request</a>.</dd>
    <dd>This term was taken verbatim from <a href="#ref-wca-terms">Web
      Characterization Terminology &amp; Definitions Sheet</a>.</dd>
  <dt><a name="def-server" id="def-server">Server</a></dt>
    <dd class="verbatim">The role adopted by an application when it is
      supplying <a href="#def-resource">resources</a> or <a
      href="#def-resource-manifestation">resource manifestations</a>.</dd>
    <dd>This term was taken verbatim from <a href="#ref-wca-terms">Web
      Characterization Terminology &amp; Definitions Sheet</a>.</dd>
  <dt><a name="def-single-authoring" id="def-single-authoring">Single
  Authoring</a></dt>
    <dd class="">An authoring style in which a single <a
      href="#def-variant">variant</a> of each <a
      href="#def-resource">resource</a> is created and is automatically <a
      href="#def-adaptation">adapted</a> to produce the <a
      href="#def-user-experience">user experience</a> for each <a
      href="#def-delivery-context-v2">delivery context</a>. .</dd>
    <dd class="">Single authoring represents one end of a spectrum of
      authoring styles that include <a
      href="#def-multiple-authoring">multiple authoring</a> and <a
      href="#def-flexible-authoring">flexible authoring</a>. It represents a
      theoretical extreme that is rarely achieved in practice. Though,
      theoretically, it offers the minimum development cost, limitations in
      practical adaptation systems mean that compromises are necessary in the
      final user experiences. These compromises are often considered
      unacceptable.</dd>
  <dt><a name="def-uniform-resource-identifier"
  id="def-uniform-resource-identifier">Uniform Resource Identifier</a></dt>
    <dd>A short string that uniquely identifies a <a
      href="#def-resource">resource</a> such as an HTML document, an image, a
      down-loadable file, a service, or an electronic mailbox.</dd>
  <dt><a name="def-user" id="def-user">User</a></dt>
    <dd>A human who perceives and <a href="#def-interaction">interacts</a>
      with the web</dd>
  <dt><a name="def-user-agent" id="def-user-agent">User Agent</a></dt>
    <dd>A <a href="#def-client">client</a> within a <a
      href="#def-device">device</a> that performs <a
      href="#def-rendering">rendering</a>.</dd>
    <dd>Browsers are examples of <a href="#def-user-agent">user agents</a>,
      as are web robots that automatically traverse the web collecting
      information.</dd>
  <dt><a name="def-user-experience" id="def-user-experience">User
  Experience</a></dt>
    <dd>A set of material <a href="#def-rendering">rendered</a> by a <a
      href="#def-user-agent">user agent</a> which may be perceived by a <a
      href="#def-user">user</a> and with which <a
      href="#def-interaction">interaction</a> may be possible.</dd>
  <dt><a name="def-variant" id="def-variant">Variant</a></dt>
    <dd>A <a href="#def-resource">resource</a> may have one, or more than
      one, representation(s) associated with it at any given instant. Each of
      these representations is termed a `variant.' Use of the term `variant'
      does not necessarily imply that the resource is subject to <a
      href="#def-content-negotiation">content negotiation</a>.</dd>
    <dd>This term is taken verbatim from <a href="#ref-http">Hypertext
      Transfer Protocol -- HTTP/1.1</a>.</dd>
  <dt><a name="def-web-page" id="def-web-page">Web Page</a></dt>
    <dd>A collection of information, consisting of one or more <a
      href="#def-resource">resources</a>, intended to be rendered
      simultaneously, and identified by a single <a
      href="#def-uniform-resource-identifier">Uniform Resource
    Identifier</a>.</dd>
    <dd>More specifically, a web page consists of a <a
      href="#def-resource">resource</a> with zero, one, or more embedded <a
      href="#def-resource">resources</a> intended to be rendered as a single
      unit, and referred to by the <a
      href="#def-uniform-resource-identifier">URI</a> of the one <a
      href="#def-resource">resource</a> which is not embedded.</dd>
    <dd>This term was developed from the definition of <strong>web
      page</strong> in <a href="#ref-wca-terms">Web Characterization
      Terminology &amp; Definitions Sheet</a>.</dd>
  <dt><a name="def-web-page-identifier" id="def-web-page-identifier">Web Page
  Identifier</a></dt>
    <dd>A <a href="#def-uniform-resource-identifier">Uniform Resource
      Identifier</a> intended to be recognized by a user as representing the
      identity of a specific Web Page (resource).</dd>
    <dd>It may need to be entered explicitly by a user.</dd>
</dl>

<h2><a name="sec-using-and-maintaining" id="sec-using-and-maintaining">A
Using and Maintaining the Glossary</a></h2>

<p>This section documents the way in which the glossary should be used from
other DIWG documents. It also documents how changes are to be made to the
glossary itself in a way that will not invalidate links to the
definitions.</p>

<h3><a name="sec-using" id="sec-using">A.1 Using the Glossary</a></h3>

<p>Every definition in the glossary has an associated anchor. As a
consequence every definition can be directly referenced externally from other
documents. Such references should use the public URL associated with the DIWG
glossary. For the latest version of the glossary, this has been established
as <br />
<br />
<a
href="http://www.w3.org/TR/di-gloss/">http://www.w3.org/TR/di-gloss/</a></p>

<p>Dated versions of the glossary will appear at URLs in the form of the
following <br />
<br />
<a
href="http://www.w3.org/TR/2003/WD-di-gloss-20030825/">http://www.w3.org/TR/2003/WD-di-gloss-20030825/</a></p>

<p>To refer to a particular definition, a document should create a URL based
on the appropriately dated, public URL and the fragment identifier for the
definition. Fragment identifiers consist of the definition name, in
lowercase, with words separated by dashes and prefixed by
<strong>def</strong>. For example, the fragment identifier for the definition
of <strong>User Agent</strong> is <strong>def-user-agent</strong>, and for
<strong>Navigation</strong> is <strong>def-navigation</strong>. The URL to
use for the definition of Navigation for the dated version mentioned above
would be: <br />
<br />
<a
href="http://www.w3.org/TR/2003/WD-di-gloss-20030825/#def-navigation">http://www.w3.org/TR/2003/WD-di-gloss-20030825/#def-navigation</a></p>

<p>One important guarantee for documents that reference the glossary is that
the fragment identifier for a given definition never changes. If, for
example, a new version of a particular definition is needed, the older
version will be retained within the glossary with its fragment identifier.
The new version will be given a new identifier. The process used to maintain
the glossary and to retain this uniqueness of definition identifiers is
described in the following section.</p>

<p>In addition to referring directly to individual definitions in the
glossary, documents that use it should include a reference to the dated
version in use in their References section. The following is an example of
such a reference:</p>
<dl>
  <dt class="label"><a name="ref-di-gloss" id="ref-di-gloss"></a> Glossary of
  Terms for Device Independence (version used for definitions)</dt>
    <dd><a
      href="http://www.w3.org/TR/2003/WD-di-gloss-20030825/"><cite>Glossary
      of Terms for Device Independence</cite></a>, Rhys Lewis, 2003. W3C
      Working Draft available at:
      http://www.w3.org/TR/2003/WD-di-gloss-20030825/</dd>
</dl>

<h3><a name="sec-maintaining" id="sec-maintaining">A.2 Maintaining the
Glossary</a></h3>

<p>The DIWG glossary will remain a public working draft. This reflects the
need to update it as new work is carried out in DIWG. The need to revise the
glossary, and in particular the potential requirement to revise definitions,
leads to a need for a mechanism that can allow older documents to refer
unambiguously to older revisions of particular definitions.</p>

<p>Once a version of the glossary has been published, the definitions it
contains have fragment identifiers that must not be changed. As new
definitions are added they are given new identifiers. This poses no issues
for documents authored before the new definitions were published. However,
when a definition is revised, it is vital that older documents that used the
old version are still valid. They are protected by the use of version
identification within the fragment identifiers. In addition, the old versions
of definitions are maintained in <a href="#sec-previous-versions">Appendix
B</a> of the glossary.</p>

<p>To revise a glossary definition, the following steps must be carried
out:</p>
<ol>
  <li>The existing definition, complete with fragment identifier, must be
    copied to <a href="#sec-previous-versions">Appendix B</a>.</li>
  <li>The definition must be updated within the main part of the
  glossary.</li>
  <li>The revised definition must be given an updated fragment identifier
    constructed by adding a version number where none exists, or incrementing
    it if one already exists. For example, if the fragment identifier before
    revision were <strong>#def-navigation</strong> it would become <strong><a
    name="def-navigation-v2"
    id="def-navigation-v2">#def-navigation-v2</a></strong>. Alternatively, if
    the fragment identifier before revision were
    <strong>#def-navigation-v7</strong> it would become
    <strong>#def-navigation-v8</strong>.</li>
  <li><strong>All</strong> references to the definition within the glossary
    itself must be updated to refer to this new fragment identifier. In
    addition, all definitions that refer to the revised definition must be
    reviewed to see whether they need modification because of the change. If
    so, this same procedure must be applied those definitions and new
    versions must be created.</li>
  <li>The old definition that has been moved to <a
    href="#sec-previous-versions">Appendix B</a> must have a reference added
    that refers to the newer definition in the body of the glossary. As an
    example, the reference for an old version of the definition of Navigation
    might include the reference: <br />
    <br />
    "This definition has been superseded. There is a newer definition of <a
    href="#def-navigation-v2">Navigation</a>". <br />
    <br />
    Notice that <em>these</em> links should <strong>not</strong> be updated
    when a new version of a definition is added. By not changing them, they
    form a chain through the versions of the definition from the one
    referenced by the external document up to the latest version.</li>
</ol>

<h2><a name="sec-previous-versions" id="sec-previous-versions">B Previous
Versions of Definitions</a></h2>

<p>This section contains definitions that have been superseded within the
existing glossary. The first section holds definitions that have been
updated. The second section holds definitions that have been removed.</p>

<h3><a name="sec-updated" id="sec-updated">B.1 Definitions that Have Been
Updated</a></h3>
<dl>
  <dt><a name="def-delivery-context" id="def-delivery-context">Delivery
  Context</a></dt>
    <dd class="">A set of attributes that characterizes the capabilities of
      the <a href="#def-access-mechanism">access mechanism</a>, and the
      preferences of the <a href="#def-user">user</a>. This definition has
      been superseded. There is a new definition of <a
      href="#def-delivery-context-v2">Delivery Context</a>.</dd>
  <dt><a name="def-decomposition"
  id="def-decomposition">Decomposition</a></dt>
    <dd>The act of dividing up one or more <a
      href="#def-authored-unit">authored units</a> during creation of a set
      of <a href="#def-perceivable-unit">perceivable units</a> appropriate
      for a particular delivery context. This definition has been superseded.
      There is a new definition of <a
      href="#def-decomposition-v2">decomposition</a>.</dd>
</dl>

<h3><a name="sec-removed" id="sec-removed">B.2 Definitions that Have Been
Removed</a></h3>
<dl>
  <dt><a name="def-user-experience-preferences"
  id="def-user-experience-preferences">User Experience Preferences</a></dt>
    <dd>A set of preferences, specified by a <a href="#def-user">user</a>,
      that affect the <a href="#def-user-experience">user experience</a> that
      results from <a href="#def-adaptation">adaptation</a> for a given <a
      href="#def-delivery-context-v2">delivery context</a></dd>
  <dt><a name="def-fragmentation"
  id="def-fragmentation">Fragmentation</a></dt>
    <dd>The act of dividing up one or more <a
      href="#def-authored-unit">authored units</a> to create a set of <a
      href="#def-perceivable-unit">perceivable units</a> appropriate for a
      particular delivery context. This term has been replaced by the new
      term <a href="#def-decomposition">decomposition</a></dd>
</dl>

<h3><a name="sec-deprecated" id="sec-deprecated">B.3 Definitions that Have
Been Deprecated</a></h3>

<p>No definitions have yet been deprecated.</p>

<h2><a name="sec-references" id="sec-references">C References</a></h2>
<dl>
  <dt class="label"><a name="ref-http" id="ref-http">Hypertext Transfer
  Protocol -- HTTP/1.1.1</a></dt>
    <dd><a
      href="http://www.w3.org/Protocols/rfc2616/rfc2616.html"><cite>Hypertext
      Transfer Protocol -- HTTP/1.1</cite></a>, June 1999. IETF RFC-2616
      available at http://www.w3.org/Protocols/rfc2616/rfc2616.html</dd>
  <dt class="label"><a name="ref-urisyn" id="ref-urisyn">Uniform Resource
  Identifiers (URI): Generic Syntax</a></dt>
    <dd><a href="http://www.ietf.org/rfc/rfc2396.txt"><cite>Uniform Resource
      Identifiers (URI): Generic Syntax</cite></a>, June 1998. IETF RFC-2396
      available at http://www.ietf.org/rfc/rfc2396.txt</dd>
  <dt class="label"><a name="ref-uri" id="ref-uri">Naming and Addressing:
  URIs, URLs, ...</a></dt>
    <dd><a href="http://www.w3.org/Addressing/"><cite>Naming and Addressing:
      URIs, URLs, ...</cite></a> available at
    http://www.w3.org/Addressing/</dd>
  <dt class="label"><a name="ref-wca-terms" id="ref-wca-terms">Web
  Characterization Terminology &amp; Definitions Sheet</a></dt>
    <dd><a href="http://www.w3.org/1999/05/WCA-terms/"><cite>Web
      Characterization Terminology &amp; Definitions Sheet</cite></a>, May
      1999. W3C Working Draft available at
      http://www.w3.org/1999/05/WCA-terms/</dd>
  <dt class="label"><a name="weaving-web" id="weaving-web">Weaving the Web:
  Glossary</a></dt>
    <dd><a
      href="http://www.w3.org/People/Berners-Lee/Weaving/glossary.html"><cite>Weaving
      the Web: Glossary</cite></a>, 1999, Tim Berners-Lee. Available at
      http://www.w3.org/People/Berners-Lee/Weaving/glossary.html</dd>
</dl>

<h2><a name="sec-acknowledgements" id="sec-acknowledgements">D
Acknowledgments</a></h2>

<p>Members of the W3C Device Independence Working Group have helped develop
this Working Draft through their comments, proposals and discussions at
teleconferences, face-to-face meetings and via the group discussion list.</p>

<p>At the time of publication, the principal and active members of the group
were as follows:</p>
<dl>
    <dd>Stephane Boyera (W3C)</dd>
    <dd>Roger Gimson (HP)</dd>
    <dd>Mark Butler (HP)</dd>
    <dd>Rotan Hanrahan (MobileAware Ltd)</dd>
    <dd>Kazuhiro Kitagawa (W3C)</dd>
    <dd>Augusto Aguilera (Boeing)</dd>
    <dd>Cedric Ulmer (SAP)</dd>
    <dd>Rhys Lewis (Volantis Systems Ltd)</dd>
    <dd>Roland Merrick (IBM)</dd>
    <dd>Andreas Schade (IBM)</dd>
    <dd>Gabriel Guillaume (France Telecom)</dd>
    <dd>Fabio Paterno (CNR--Instituto Elaborazione dell'Informazione)</dd>
</dl>

<p>The following were members of the group at earlier stages of its
drafting:</p>
<dl>
    <dd>Shahid Shoaib (NTT DoCoMo)</dd>
    <dd>Ryuji Tamagawa (Sky Co. Ltd.)</dd>
    <dd>Greg Ziebold (Sun Microsystems)</dd>
    <dd>Yoshihisa Gonno (Sony Corp)</dd>
    <dd>Luu Tran (Sun Microsystems)</dd>
    <dd>Michael Wasmund (IBM)</dd>
    <dd>Jason White (University of Melbourne)</dd>
    <dd>Masashi Morioka (NTT DoCoMo)Tayeb Lemlouma (INRIA)</dd>
    <dd>Guido Grassel (Nokia)</dd>
    <dd>Amy Yu (SAP AG)</dd>
    <dd>Candy Wong (NTT DoCoMo)</dd>
    <dd>Stan Wiechers (Merkwelt)</dd>
    <dd>Franklin Reynolds (Nokia)</dd>
    <dd>Markus Lauff (SAP AG)</dd>
    <dd>Steve Farowich (Boeing)</dd>
    <dd>Yasser AlSafadi (Philips Research)</dd>
    <dd>Abbie Barbir (Nortel Networks)</dd>
    <dd>Einar Breen (Adaptive Media)</dd>
    <dd>Shlomit Ritz Finkelstein (invited expert)</dd>
    <dd>Vidhya Golkar (Argogroup)</dd>
    <dd>Luo Haiping (Comverse)</dd>
    <dd>Eric Hsi (Philips Research)</dd>
    <dd>Lynda Jones (SHARE)</dd>
    <dd>William Loughborough (Smith-Kettlewell Institute)</dd>
    <dd>Stephane Maes (IBM)</dd>
    <dd>Kaori Nakai (NTT DoCoMo)</dd>
    <dd>Hidetaka Ohto (W3C/Panasonic)</dd>
    <dd>Garland Phillips (Motorola)</dd>
    <dd>Lalitha Suryanarayana (SBC Technology Resources)</dd>
    <dd>Yoshifumi Yonemoto (NTT DoCoMo)</dd>
</dl>
<hr />
</body>
</html>