W3C home > Mailing lists > Public > public-sdw-wg@w3.org > February 2015

Re: Geospatial decision in W3C SVG WG: Move svg:transform mapping to its own spec

From: Andreas Harth <harth@kit.edu>
Date: Wed, 25 Feb 2015 17:51:30 +0100
Message-ID: <54EDFD92.3060509@kit.edu>
To: <public-sdw-wg@w3.org>
Hi,

would that be something to write as a use case?  If SVG with
geo is a requirement that can be derived from a use case, we
would ensure that SVG/geo shows up somewhere.  The tricky bit
is coming up with a use case that would require SVG/geo.

Cheers,
Andreas.

On 2015-02-24 11:52, Little, Chris wrote:
> Kerry, Ed,
>
> Just checking that you were aware of this activity, and perhaps we should ensure SVG with geo info embedded in metadata is included in a SDWWG deliverable at some time.
>
> Chris
>
> -----Original Message-----
> From: SVG Working Group repository [mailto:cam+svgwgrepo@mcc.id.au]
> Sent: Friday, February 13, 2015 4:21 AM
> To: w3c-svg-wg@w3.org
> Subject: [svgwg] Move svg:transform mapping to its own spec
>
> https://github.com/w3c/svgwg/commit/637ae4967c0b923a97c5c8f82ac530d44823d1a3
> commit 637ae4967c0b923a97c5c8f82ac530d44823d1a3
> Author: Dirk Schulze <dschulze@chromium.org>
> Date:   Fri Feb 13 15:18:27 2015 +1100
>
>      Move svg:transform mapping to its own spec
>
> diff --git a/master/coords.html b/master/coords.html
> index ecf00e8..be645c1 100644
> --- a/master/coords.html
> +++ b/master/coords.html
> @@ -1574,44 +1574,6 @@ object within a containing block that is only constrained in one direction.</p>
>   <a href="https://docs.google.com/presentation/d/1POUiroOBbLmXYlQKf0pIR8zVkHWH9jRVN-w8A4aNsIk/">examples</a>
>   provided by David Vest.</p>
>
> -<h2 id="GeographicCoordinates">Geographic coordinate systems</h2>
> -
> -<p>In order to allow interoperability between SVG content generators
> -and user agents dealing with maps encoded in SVG, the use of a common
> -metadata definition for describing the coordinate system used to
> -generate SVG documents is encouraged.</p>
> -
> -<p>Such metadata must be added under the <a>'metadata'</a> element of
> -the topmost <a>'svg'</a> element describing the map, consisting of an
> -RDF description of the Coordinate Reference System definition used to
> -generate the SVG map [<a href='refs.html#ref-RDF-PRIMER'>RDF-PRIMER</a>]. Note that
> -the presence of this metadata does not affect the rendering of the SVG
> -in any way; it merely provides added semantic value for applications
> -that make use of combined maps.</p>
> -
> -<p>The definition must be conformant to the XML grammar described in
> -<a href="http://portal.opengeospatial.org/files/?artifact_id=20509"><cite>GML 3.2.1</cite></a>,
> -an OpenGIS Standard for encoding common CRS data types in XML
> -[<a href='refs.html#ref-GML'>GML</a>]. In order to correctly map
> -the 2-dimensional data used by SVG, the CRS must be of subtype
> -<strong>ProjectedCRS</strong> or <strong>Geographic2dCRS</strong>. The
> -first axis of the described CRS maps the SVG <var>x</var>-axis and the
> -second axis maps the SVG <var>y</var>-axis.</p>
> -
> -<p>The main purpose of such metadata is to indicate to the user agent
> -that two or more SVG documents can be overlayed or merged into a single
> -document. Obviously, if two maps reference the same Coordinate Reference
> -System definition and have the same SVG <a>'transform'</a> property
> -value then they can be overlayed without reprojecting the data. If
> -the maps reference different Coordinate Reference Systems and/or have
> -different SVG <a>'transform'</a> property values, then a specialized
> -cartographic user agent may choose to transform the coordinate data to
> -overlay the data. However, typical SVG user agents are not required
> -to perform these types of transformations, or even recognize the
> -metadata. It is described in this specification so that the connection
> -between geographic coordinate systems and the SVG coordinate system is
> -clear.</p>
> -
>   <h2 id="DOMInterfaces">DOM interfaces</h2>
>
>   <h3 id="InterfaceSVGPointList">Interface SVGPointList</h3>
> @@ -2052,8 +2014,6 @@ interface <b>SVGTransform</b> {
>             <p>If <var>value</var> could not be parsed as a
>             <a>&lt;transform-function&gt;</a>, then a <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#syntaxerror">SyntaxError</a>
>             is thrown.</p>
> -          <p class='issue'>The CSS Transforms specification does not have
> -          a grammar for <a>&lt;transform-function&gt;</a> yet.</p>
>           </div>
>         </dd>
>       </dl>
> diff --git a/specs/transform/Overview.bs b/specs/transform/Overview.bs
> new file mode 100644
> index 0000000..4c1c144
> --- /dev/null
> +++ b/specs/transform/Overview.bs
> @@ -0,0 +1,325 @@
> +<h1>svg:transform for mapping</h1>
> +<pre class='metadata'>
> +Level: 1
> +Status: ED
> +ED: http://dev.w3.org/fxtf/motion-1/
> +Shortname: transform-mapping
> +Group: svg
> +Editor: Satoru Takagi, KDDI Corporation, sa-takagi@kddi.com
> +Abstract: This specification gives guidance how the SVG transform attribute in the SVG namespace can be used in other context than SVG.
> +</pre>
> +<pre class=link-defaults>
> +spec:svg2; type:element; text:svg
> +spec:css-transforms-1; type:property; text:transform
> +spec:css-transforms-1; type:type; text:<transform-list>
> +</pre>
> +
> +<h2 id="GeographicCoordinates">Geographic coordinate systems</h2>
> +
> +In order to allow interoperability between SVG content generators
> +and user agents dealing with maps encoded in SVG, the use of a common
> +metadata definition for describing the coordinate system used to
> +generate SVG documents is encouraged.
> +
> +Such metadata must be added under the <a element>metadata</a> element of
> +the topmost <a element>svg</a> element describing the map, consisting of an
> +RDF description of the Coordinate Reference System definition used to
> +generate the SVG map [[RDF-PRIMER]]. Note that
> +the presence of this metadata does not affect the rendering of the SVG
> +in any way; it merely provides added semantic value for applications
> +that make use of combined maps.
> +
> +The definition must be conformant to the XML grammar described in
> +<a href="http://portal.opengeospatial.org/files/?artifact_id=20509"><cite>GML 3.2.1</cite></a>,
> +an OpenGIS Standard for encoding common CRS data types in XML
> +[<a href='refs.html#ref-GML'>GML</a>]. In order to correctly map
> +the 2-dimensional data used by SVG, the CRS must be of subtype
> +<strong>ProjectedCRS</strong> or <strong>Geographic2dCRS</strong>. The
> +first axis of the described CRS maps the SVG <var>x</var>-axis and the
> +second axis maps the SVG <var>y</var>-axis.
> +
> +The main purpose of such metadata is to indicate to the user agent
> +that two or more SVG documents can be overlayed or merged into a single
> +document. Obviously, if two maps reference the same Coordinate Reference
> +System definition and have the same SVG 'transform' property
> +value then they can be overlayed without reprojecting the data. If
> +the maps reference different Coordinate Reference Systems and/or have
> +different SVG 'transform' property values, then a specialized
> +cartographic user agent may choose to transform the coordinate data to
> +overlay the data. However, typical SVG user agents are not required
> +to perform these types of transformations, or even recognize the
> +metadata. It is described in this specification so that the connection
> +between geographic coordinate systems and the SVG coordinate system is
> +clear.
> +
> +<h2 id="SVGGlobalTransformAttribute">The <span class="attr-name">'svg:transform'</span> attribute</h2>
> +
> +<div class="adef-list">
> +  <p><em>Attribute definition:</em></p>
> +  <dl>
> +    <dt id="SVGGlobalTransformAttributeDefinition"><dfn>svg:transform</dfn> = <<transform-list>> | ''transform/none''</dt>
> +    <dd>
> +      <dl>
> +        <dt><<transform-list>></dt>
> +        <dd>
> +          <p>Specifies the affine transformation that has been
> +          applied to the map data. The syntax is identical to
> +          that described for the 'transform' property.</p>
> +        </dd>
> +
> +        <dt><span class="attr-value">none</span></dt>
> +        <dd>
> +          <p>Specifies that no supplemental affine transformation has been
> +          applied to the map data.  Using this value has the same meaning as
> +          specifying the identity matrix, which in turn is just the same as
> +          not specifying the <a>svg:transform</a> the attribute at all.</p>
> +        </dd>
> +      </dl>
> +      <p class="anim-target">Animatable: no.</p>
> +    </dd>
> +  </dl>
> +</div>
> +
> +This attribute describes an optional additional affine
> +transformation that may have been applied during this
> +mapping. This attribute may be added to the OpenGIS
> +<em>CoordinateReferenceSystem</em> element. Note
> +that, unlike the 'transform' property, it does not indicate that
> +a transformation is to <em>be applied</em> to the data within the file.
> +Instead, it simply describes the transformation that <em>was already
> +applied</em> to the data when being encoded in SVG.
> +
> +There are three typical uses for the <a>svg:transform</a>
> +global attribute. These are described below and used in the examples.
> +
> +<ul>
> +  <li>Most ProjectedCRS have the north direction represented by
> +  positive values of the second axis and conversely SVG has a
> +  <var>y</var>-down coordinate system. That's why, in order to follow the
> +  usual way to represent a map with the north at its top, it is
> +  recommended for that kind of ProjectedCRS to use the
> +  <a>svg:transform</a>
> +  global attribute with a ''scale(1, -1)'' value as in the
> +  third example below.</li>
> +
> +  <li>Most Geographic2dCRS have the latitude as their first
> +  axis rather than the longitude, which means that the
> +  south-north axis would be represented by the <var>x</var>-axis in SVG
> +  instead of the usual <var>y</var>-axis. That's why, in order to follow
> +  the usual way to represent a map with the north at its top,
> +  it is recommended for that kind of Geographic2dCRS to use the
> +  <a>svg:transform'</a>
> +  global attribute with a ''rotate(-90)'' value as in the
> +  first example (while also adding the ''scale(1, -1)'' as for
> +  ProjectedCRS).</li>
> +
> +  <li>In addition, when converting for profiles which place
> +  restrictions on precision of real number values, it may be
> +  useful to add an additional scaling factor to retain good
> +  precision for a specific area. When generating an SVG
> +  document from WGS84 geographic coordinates (EPGS 4326), we
> +  recommend the use of an additional 100 times scaling factor
> +  corresponding to an <a>svg:transform</a>
> +  global attribute with a ''rotate(-90) scale(100)''
> +  value (shown in the second example).
> +  Different scaling values may be required depending on the
> +  particular CRS.</li>
> +</ul>
> +
> +Below is a simple example of the coordinate metadata, which
> +describes the coordinate system used by the document via a
> +URI.
> +
> +<div class="example">
> + <pre><code class=html>
> +&lt;?xml version="1.0"?>
> +&lt;svg xmlns="http://www.w3.org/2000/svg"
> +     width="100" height="100" viewBox="0 0 1000 1000">
> +
> +  &lt;desc>An example that references coordinate data.&lt;/desc>
> +
> +  &lt;metadata>
> +    &lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> +             xmlns:crs="http://www.ogc.org/crs"
> +             xmlns:svg="http://www.w3.org/2000/svg">
> +      &lt;rdf:Description rdf:about="">
> +        &lt;!-- The Coordinate Reference System is described
> +             through a URI. -->
> +        &lt;crs:CoordinateReferenceSystem
> +            svg:transform="rotate(-90)"
> +            rdf:resource="http://www.example.org/srs/epsg.xml#4326"/>
> +      &lt;/rdf:Description>
> +    &lt;/rdf:RDF>
> +  &lt;/metadata>
> +
> +  &lt;!-- The actual map content -->
> +&lt;/svg>
> +</code></pre>
> +</div>
> +
> +The second example uses a well-known identifier to describe
> +the coordinate system. Note that the coordinates used in the
> +document have had the supplied transform applied.
> +
> +<div class="example">
> +  <pre><code class=html>
> +&lt;?xml version="1.0"?>
> +&lt;svg xmlns="http://www.w3.org/2000/svg"
> +     width="100" height="100" viewBox="0 0 1000 1000">
> +
> +  &lt;desc>Example using a well known coordinate system.&lt;/desc>
> +
> +  &lt;metadata>
> +    &lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> +             xmlns:crs="http://www.ogc.org/crs"
> +             xmlns:svg="http://www.w3.org/2000/svg">
> +      &lt;rdf:Description rdf:about="">
> +        &lt;!-- In case of a well-known Coordinate Reference System
> +             an 'Identifier' is enough to describe the CRS -->
> +        &lt;crs:CoordinateReferenceSystem svg:transform="rotate(-90) scale(100, 100)">
> +          &lt;crs:Identifier>
> +            &lt;crs:code>4326&lt;/crs:code>
> +            &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +            &lt;crs:edition>5.2&lt;/crs:edition>
> +          &lt;/crs:Identifier>
> +        &lt;/crs:CoordinateReferenceSystem>
> +      &lt;/rdf:Description>
> +    &lt;/rdf:RDF>
> +  &lt;/metadata>
> +
> +  &lt;!-- The actual map content -->
> +&lt;/svg>
> +  </code></pre>
> +</div>
> +
> +The third example defines the coordinate system completely
> +within the SVG document.
> +
> +<div class="example">
> +  <pre><code class=html>
> +&lt;?xml version="1.0"?>
> +&lt;svg xmlns="http://www.w3.org/2000/svg"
> +     width="100" height="100" viewBox="0 0 1000 1000">
> +
> +  &lt;desc>Coordinate metadata defined within the SVG document&lt;/desc>
> +
> +  &lt;metadata>
> +    &lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> +             xmlns:crs="http://www.ogc.org/crs"
> +             xmlns:svg="http://www.w3.org/2000/svg">
> +      &lt;rdf:Description rdf:about="">
> +        &lt;!-- For other CRS it should be entirely defined -->
> +        &lt;crs:CoordinateReferenceSystem svg:transform="scale(1,-1)">
> +          &lt;crs:NameSet>
> +            &lt;crs:name>Mercator projection of WGS84&lt;/crs:name>
> +          &lt;/crs:NameSet>
> +          &lt;crs:ProjectedCRS>
> +            &lt;!-- The actual definition of the CRS -->
> +            &lt;crs:CartesianCoordinateSystem>
> +              &lt;crs:dimension>2&lt;/crs:dimension>
> +              &lt;crs:CoordinateAxis>
> +                &lt;crs:axisDirection>north&lt;/crs:axisDirection>
> +                &lt;crs:AngularUnit>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>9108&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                &lt;/crs:AngularUnit>
> +              &lt;/crs:CoordinateAxis>
> +              &lt;crs:CoordinateAxis>
> +                &lt;crs:axisDirection>east&lt;/crs:axisDirection>
> +                &lt;crs:AngularUnit>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>9108&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                &lt;/crs:AngularUnit>
> +              &lt;/crs:CoordinateAxis>
> +            &lt;/crs:CartesianCoordinateSystem>
> +            &lt;crs:CoordinateReferenceSystem>
> +              &lt;!-- the reference system of that projected system is
> +                         WGS84 which is EPSG 4326 in EPSG codeSpace -->
> +              &lt;crs:NameSet>
> +                &lt;crs:name>WGS 84&lt;/crs:name>
> +              &lt;/crs:NameSet>
> +              &lt;crs:Identifier>
> +                &lt;crs:code>4326&lt;/crs:code>
> +                &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                &lt;crs:edition>5.2&lt;/crs:edition>
> +              &lt;/crs:Identifier>
> +            &lt;/crs:CoordinateReferenceSystem>
> +            &lt;crs:CoordinateTransformationDefinition>
> +              &lt;crs:sourceDimensions>2&lt;/crs:sourceDimensions>
> +              &lt;crs:targetDimensions>2&lt;/crs:targetDimensions>
> +              &lt;crs:ParameterizedTransformation>
> +                &lt;crs:TransformationMethod>
> +                  &lt;!-- the projection is a Mercator projection which is
> +                        EPSG 9805 in EPSG codeSpace -->
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>Mercator&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>9805&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:description>Mercator (2SP)&lt;/crs:description>
> +                &lt;/crs:TransformationMethod>
> +                &lt;crs:Parameter>
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>Latitude of 1st standart parallel&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>8823&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:value>0&lt;/crs:value>
> +                &lt;/crs:Parameter>
> +                &lt;crs:Parameter>
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>Longitude of natural origin&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>8802&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:value>0&lt;/crs:value>
> +                &lt;/crs:Parameter>
> +                &lt;crs:Parameter>
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>False Easting&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>8806&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:value>0&lt;/crs:value>
> +                &lt;/crs:Parameter>
> +                &lt;crs:Parameter>
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>False Northing&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>8807&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:value>0&lt;/crs:value>
> +                &lt;/crs:Parameter>
> +              &lt;/crs:ParameterizedTransformation>
> +            &lt;/crs:CoordinateTransformationDefinition>
> +          &lt;/crs:ProjectedCRS>
> +        &lt;/crs:CoordinateReferenceSystem>
> +      &lt;/rdf:Description>
> +    &lt;/rdf:RDF>
> +  &lt;/metadata>
> +
> +  &lt;!-- the actual map content -->
> +&lt;/svg>
> +  </code></pre>
> +</div>
> \ No newline at end of file
> diff --git a/specs/transform/Overview.html b/specs/transform/Overview.html
> new file mode 100644
> index 0000000..2510f34
> --- /dev/null
> +++ b/specs/transform/Overview.html
> @@ -0,0 +1,681 @@
> +<!doctype html>
> +<html lang="en">
> + <head>
> +
> +  <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
> +
> +
> +  <title>svg:transform for mapping</title>
> +
> +
> +  <link href="../default.css" rel="stylesheet" type="text/css">
> +
> +
> +  <link href="https://www.w3.org/StyleSheets/TR/W3C-ED" rel="stylesheet" type="text/css">
> +
> +
> +  <meta content="Bikeshed 1.0.0" name="generator">
> + </head>
> +
> +
> + <body class="h-entry">
> +
> +  <div class="head">
> +
> +   <p data-fill-with="logo"></p>
> +
> +   <h1 class="p-name no-ref" id="title">svg:transform for mapping</h1>
> +
> +   <h2 class="no-num no-toc no-ref heading settled" id="subtitle"><span class="content">Editor’s Draft,
> +    <time class="dt-updated" datetime="2015-02-13">13 February 2015</time></span></h2>
> +
> +   <div data-fill-with="spec-metadata">
> +    <dl>
> +     <dt>This version:
> +     <dd><a class="u-url" href="http://dev.w3.org/fxtf/motion-1/">http://dev.w3.org/fxtf/motion-1/</a>
> +     <dt>Feedback:
> +     <dd><span><a href="mailto:www-svg@w3.org?subject=%5Btransform-mapping%5D%20feedback">www-svg@w3.org</a> with subject line “<kbd>[transform-mapping] <var>… message topic …</var></kbd>” (<a href="http://lists.w3.org/Archives/Public/www-svg/" rel="discussion">archives</a>)</span>
> +     <dt class="editor">Editor:
> +     <dd class="editor">
> +      <div class="p-author h-card vcard"><a class="p-name fn u-email email" href="mailto:sa-takagi@kddi.com">Satoru Takagi</a> (<span class="p-org org">KDDI Corporation</span>)</div>
> +    </dl>
> +   </div>
> +
> +   <div data-fill-with="warning"></div>
> +
> +   <p class="copyright" data-fill-with="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2015 <a href="http://www.w3.org/"><abbr title="World Wide Web Consortium">W3C</abbr></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><abbr title="Massachusetts Institute of Technology">MIT</abbr></a>, <a href="http://www.ercim.eu/"><abbr title="European Research Consortium for Informatics and Mathematics">ERCIM</abbr></a>, <a href="http://www.keio.ac.jp/">Keio</a>, <a href="http://ev.buaa.edu.cn/">Beihang</a>). W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.
> +</p>
> +
> +   <hr title="Separator for header">
> +</div>
> +
> +
> +  <h2 class="no-num no-toc no-ref heading settled" id="abstract"><span class="content">Abstract</span></h2>
> +
> +  <div class="p-summary" data-fill-with="abstract">
> +   <p>This specification gives guidance how the SVG transform attribute in the SVG namespace can be used in other context than SVG.</p>
> +
> +</div>
> +
> +
> +  <h2 class="no-num no-toc no-ref heading settled" id="status"><span class="content">Status of this document</span></h2>
> +
> +  <div data-fill-with="status">
> +   <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 at http://www.w3.org/TR/.</a></em>
> +
> +</p>
> +   <p>
> +       This document is the 13 February 2015 <strong>Editor’s Draft</strong> of svg:transform for mapping.
> +
> +</p>
> +   <p>
> +       Comments on this Editor’s Draft are welcome. Comments can be sent to
> +       <a href="mailto:www-svg@w3.org?Subject=%5Btransform-mapping%5D%20PUT%20SUBJECT%20HERE">www-svg@w3.org</a>,
> +       the public email list for issues related to vector graphics on the Web. This list is
> +       <a href="http://lists.w3.org/Archives/Public/www-svg/">archived</a> and senders must agree to have their message
> +       publicly archived from their first posting. To subscribe send an email to
> +       <a href="mailto:www-svg-request@w3.org?Subject=subscribe">www-svg-request@w3.org</a> with the word <code>subscribe</code>
> +       in the subject line.
> +
> +</p>
> +   <p>
> +       This document has been produced by the <a href="http://www.w3.org/Graphics/SVG/WG">SVG Working Group</a> as part of the
> +       <a href="http://www.w3.org/Graphics/Activity">Graphics Activity</a> within the
> +       <a href="http://www.w3.org/Interaction/">W3C Interaction Domain</a>. The goals of the W3C SVG Working Group are discussed in the
> +       <a href="http://www.w3.org/2007/11/SVG_rechartering/SVG-WG-charter.html">W3C SVG Charter</a>. The W3C SVG Working Group maintains a
> +       public Web page, <a href="http://www.w3.org/Graphics/SVG/">http://www.w3.org/Graphics/SVG/</a>, that contains further
> +       background information. The authors of this document are the SVG Working Group participants.
> +
> +</p>
> +   <p>
> +       This document was produced by a group operating under
> +       the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent Policy</a>.
> +       W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/19480/status" rel="disclosure">public list of any patent disclosures</a>
> +       made in connection with the deliverables of each group;
> +       these pages also includes instructions for disclosing a patent.
> +       An individual who has actual knowledge of a patent which the individual believes contains
> +       <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a>
> +       must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the W3C Patent Policy</a>.
> +
> +</p>
> +   <p>
> +       A list of current W3C Recommendations and other technical documents can be found at
> +       <a href="http://www.w3.org/TR/">http://www.w3.org/TR/</a>. W3C publications may be updated, replaced, or
> +       obsoleted by other documents at any time.
> +</p></div>
> +
> +  <div data-fill-with="at-risk"></div>
> +
> +
> +  <h2 class="no-num no-toc no-ref heading settled" id="contents"><span class="content">Table of contents</span></h2>
> +
> +  <div data-fill-with="table-of-contents" role="navigation">
> +   <ul class="toc" role="directory">
> +    <li><a href="#GeographicCoordinates"><span class="secno">1</span> <span class="content">Geographic coordinate systems</span></a>
> +    <li><a href="#SVGGlobalTransformAttribute"><span class="secno">2</span> <span class="content">The <span class="attr-name">'svg:transform'</span> attribute</span></a>
> +    <li><a href="#conformance"><span class="secno"></span> <span class="content">
> +Conformance</span></a>
> +     <ul class="toc">
> +      <li><a href="#conventions"><span class="secno"></span> <span class="content">
> +Document conventions</span></a>
> +      <li><a href="#conformance-classes"><span class="secno"></span> <span class="content">
> +Conformance classes</span></a>
> +      <li><a href="#partial"><span class="secno"></span> <span class="content">
> +Partial implementations</span></a>
> +      <li><a href="#experimental"><span class="secno"></span> <span class="content">
> +Experimental implementations</span></a>
> +      <li><a href="#testing"><span class="secno"></span> <span class="content">
> +Non-experimental implementations</span></a>
> +     </ul>
> +    <li><a href="#references"><span class="secno"></span> <span class="content">References</span></a>
> +     <ul class="toc">
> +      <li><a href="#normative"><span class="secno"></span> <span class="content">Normative References</span></a>
> +      <li><a href="#informative"><span class="secno"></span> <span class="content">Informative References</span></a>
> +     </ul>
> +    <li><a href="#index"><span class="secno"></span> <span class="content">Index</span></a>
> +   </ul></div>
> +
> +  <main>
> +
> +
> +
> +
> +
> +   <h2 class="heading settled" data-level="1" id="GeographicCoordinates"><span class="secno">1. </span><span class="content">Geographic coordinate systems</span><a class="self-link" href="#GeographicCoordinates"></a></h2>
> +
> +
> +   <p>In order to allow interoperability between SVG content generators
> +and user agents dealing with maps encoded in SVG, the use of a common
> +metadata definition for describing the coordinate system used to
> +generate SVG documents is encouraged.</p>
> +
> +
> +   <p>Such metadata must be added under the <a data-link-type="element" href="https://svgwg.org/svg2-draft/metadata.html#elementdef-metadata">metadata</a> element of
> +the topmost <a data-link-type="element" href="https://svgwg.org/svg2-draft/struct.html#NewDocument">svg</a> element describing the map, consisting of an
> +RDF description of the Coordinate Reference System definition used to
> +generate the SVG map <a data-link-type="biblio" href="#biblio-rdf-primer">[RDF-PRIMER]</a>. Note that
> +the presence of this metadata does not affect the rendering of the SVG
> +in any way; it merely provides added semantic value for applications
> +that make use of combined maps.</p>
> +
> +
> +   <p>The definition must be conformant to the XML grammar described in
> +<a href="http://portal.opengeospatial.org/files/?artifact_id=20509"><cite>GML 3.2.1</cite></a>,
> +an OpenGIS Standard for encoding common CRS data types in XML
> +[<a href="refs.html#ref-GML">GML</a>]. In order to correctly map
> +the 2-dimensional data used by SVG, the CRS must be of subtype
> +<strong>ProjectedCRS</strong> or <strong>Geographic2dCRS</strong>. The
> +first axis of the described CRS maps the SVG <var>x</var>-axis and the
> +second axis maps the SVG <var>y</var>-axis.</p>
> +
> +
> +   <p>The main purpose of such metadata is to indicate to the user agent
> +that two or more SVG documents can be overlayed or merged into a single
> +document. Obviously, if two maps reference the same Coordinate Reference
> +System definition and have the same SVG <a class="property" data-link-type="propdesc" href="http://dev.w3.org/csswg/css-transforms-1/#propdef-transform">transform</a> property
> +value then they can be overlayed without reprojecting the data. If
> +the maps reference different Coordinate Reference Systems and/or have
> +different SVG <a class="property" data-link-type="propdesc" href="http://dev.w3.org/csswg/css-transforms-1/#propdef-transform">transform</a> property values, then a specialized
> +cartographic user agent may choose to transform the coordinate data to
> +overlay the data. However, typical SVG user agents are not required
> +to perform these types of transformations, or even recognize the
> +metadata. It is described in this specification so that the connection
> +between geographic coordinate systems and the SVG coordinate system is
> +clear.</p>
> +
> +
> +   <h2 class="heading settled" data-level="2" id="SVGGlobalTransformAttribute"><span class="secno">2. </span><span class="content">The <span class="attr-name">'svg:transform'</span> attribute</span><a class="self-link" href="#SVGGlobalTransformAttribute"></a></h2>
> +
> +
> +   <div class="adef-list">
> +
> +    <p><em>Attribute definition:</em></p>
> +
> +    <dl>
> +
> +     <dt id="SVGGlobalTransformAttributeDefinition"><a class="self-link" href="#SVGGlobalTransformAttributeDefinition"></a><dfn data-dfn-type="dfn" data-noexport="" id="svgtransform">svg:transform<a class="self-link" href="#svgtransform"></a></dfn> = <a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-transforms-1/#typedef-transform-list">&lt;transform-list></a> | <span class="css">none</span>
> +
> +
> +     <dd>
> +
> +      <dl>
> +
> +       <dt><a class="production css" data-link-type="type" href="http://dev.w3.org/csswg/css-transforms-1/#typedef-transform-list">&lt;transform-list></a>
> +
> +
> +       <dd>
> +
> +        <p>Specifies the affine transformation that has been
> +          applied to the map data. The syntax is identical to
> +          that described for the <a class="property" data-link-type="propdesc" href="http://dev.w3.org/csswg/css-transforms-1/#propdef-transform">transform</a> property.</p>
> +
> +
> +
> +
> +
> +       <dt><span class="attr-value">none</span>
> +
> +
> +       <dd>
> +
> +        <p>Specifies that no supplemental affine transformation has been
> +          applied to the map data.  Using this value has the same meaning as
> +          specifying the identity matrix, which in turn is just the same as
> +          not specifying the <a data-link-type="dfn" href="#svgtransform">svg:transform</a> the attribute at all.</p>
> +
> +
> +
> +
> +      </dl>
> +
> +
> +      <p class="anim-target">Animatable: no.</p>
> +
> +
> +
> +
> +    </dl>
> +</div>
> +
> +
> +   <p>This attribute describes an optional additional affine
> +transformation that may have been applied during this
> +mapping. This attribute may be added to the OpenGIS
> +<em>CoordinateReferenceSystem</em> element. Note
> +that, unlike the <a class="property" data-link-type="propdesc" href="http://dev.w3.org/csswg/css-transforms-1/#propdef-transform">transform</a> property, it does not indicate that
> +a transformation is to <em>be applied</em> to the data within the file.
> +Instead, it simply describes the transformation that <em>was already
> +applied</em> to the data when being encoded in SVG.</p>
> +
> +
> +   <p>There are three typical uses for the <a data-link-type="dfn" href="#svgtransform">svg:transform</a>
> +global attribute. These are described below and used in the examples.</p>
> +
> +
> +   <ul>
> +
> +    <li>Most ProjectedCRS have the north direction represented by
> +  positive values of the second axis and conversely SVG has a
> +  <var>y</var>-down coordinate system. That’s why, in order to follow the
> +  usual way to represent a map with the north at its top, it is
> +  recommended for that kind of ProjectedCRS to use the
> +  <a data-link-type="dfn" href="#svgtransform">svg:transform</a>
> +  global attribute with a <span class="css">scale(1, -1)</span> value as in the
> +  third example below.
> +
> +
> +    <li>Most Geographic2dCRS have the latitude as their first
> +  axis rather than the longitude, which means that the
> +  south-north axis would be represented by the <var>x</var>-axis in SVG
> +  instead of the usual <var>y</var>-axis. That’s why, in order to follow
> +  the usual way to represent a map with the north at its top,
> +  it is recommended for that kind of Geographic2dCRS to use the
> +  <a data-link-type="dfn" href="#svgtransform">svg:transform'</a>
> +  global attribute with a <span class="css">rotate(-90)</span> value as in the
> +  first example (while also adding the <span class="css">scale(1, -1)</span> as for
> +  ProjectedCRS).
> +
> +
> +    <li>In addition, when converting for profiles which place
> +  restrictions on precision of real number values, it may be
> +  useful to add an additional scaling factor to retain good
> +  precision for a specific area. When generating an SVG
> +  document from WGS84 geographic coordinates (EPGS 4326), we
> +  recommend the use of an additional 100 times scaling factor
> +  corresponding to an <a data-link-type="dfn" href="#svgtransform">svg:transform</a>
> +  global attribute with a <span class="css">rotate(-90) scale(100)</span>
> +  value (shown in the second example).
> +  Different scaling values may be required depending on the
> +  particular CRS.
> +</ul>
> +
> +
> +   <p>Below is a simple example of the coordinate metadata, which
> +describes the coordinate system used by the document via a
> +URI.</p>
> +
> +
> +   <div class="example">
> +
> +    <pre><code class="html">&lt;?xml version="1.0"?>
> +&lt;svg xmlns="http://www.w3.org/2000/svg"
> +     width="100" height="100" viewBox="0 0 1000 1000">
> +
> +  &lt;desc>An example that references coordinate data.&lt;/desc>
> +
> +  &lt;metadata>
> +    &lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> +             xmlns:crs="http://www.ogc.org/crs"
> +             xmlns:svg="http://www.w3.org/2000/svg">
> +      &lt;rdf:Description rdf:about="">
> +        &lt;!-- The Coordinate Reference System is described
> +             through a URI. -->
> +        &lt;crs:CoordinateReferenceSystem
> +            svg:transform="rotate(-90)"
> +            rdf:resource="http://www.example.org/srs/epsg.xml#4326"/>
> +      &lt;/rdf:Description>
> +    &lt;/rdf:RDF>
> +  &lt;/metadata>
> +
> +  &lt;!-- The actual map content -->
> +&lt;/svg>
> +</code></pre>
> +</div>
> +
> +
> +   <p>The second example uses a well-known identifier to describe
> +the coordinate system. Note that the coordinates used in the
> +document have had the supplied transform applied.</p>
> +
> +
> +   <div class="example">
> +
> +    <pre><code class="html">&lt;?xml version="1.0"?>
> +&lt;svg xmlns="http://www.w3.org/2000/svg"
> +     width="100" height="100" viewBox="0 0 1000 1000">
> +
> +  &lt;desc>Example using a well known coordinate system.&lt;/desc>
> +
> +  &lt;metadata>
> +    &lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> +             xmlns:crs="http://www.ogc.org/crs"
> +             xmlns:svg="http://www.w3.org/2000/svg">
> +      &lt;rdf:Description rdf:about="">
> +        &lt;!-- In case of a well-known Coordinate Reference System
> +             an 'Identifier' is enough to describe the CRS -->
> +        &lt;crs:CoordinateReferenceSystem svg:transform="rotate(-90) scale(100, 100)">
> +          &lt;crs:Identifier>
> +            &lt;crs:code>4326&lt;/crs:code>
> +            &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +            &lt;crs:edition>5.2&lt;/crs:edition>
> +          &lt;/crs:Identifier>
> +        &lt;/crs:CoordinateReferenceSystem>
> +      &lt;/rdf:Description>
> +    &lt;/rdf:RDF>
> +  &lt;/metadata>
> +
> +  &lt;!-- The actual map content -->
> +&lt;/svg>
> +</code></pre>
> +</div>
> +
> +
> +   <p>The third example defines the coordinate system completely
> +within the SVG document.</p>
> +
> +
> +   <div class="example">
> +
> +    <pre><code class="html">&lt;?xml version="1.0"?>
> +&lt;svg xmlns="http://www.w3.org/2000/svg"
> +     width="100" height="100" viewBox="0 0 1000 1000">
> +
> +  &lt;desc>Coordinate metadata defined within the SVG document&lt;/desc>
> +
> +  &lt;metadata>
> +    &lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> +             xmlns:crs="http://www.ogc.org/crs"
> +             xmlns:svg="http://www.w3.org/2000/svg">
> +      &lt;rdf:Description rdf:about="">
> +        &lt;!-- For other CRS it should be entirely defined -->
> +        &lt;crs:CoordinateReferenceSystem svg:transform="scale(1,-1)">
> +          &lt;crs:NameSet>
> +            &lt;crs:name>Mercator projection of WGS84&lt;/crs:name>
> +          &lt;/crs:NameSet>
> +          &lt;crs:ProjectedCRS>
> +            &lt;!-- The actual definition of the CRS -->
> +            &lt;crs:CartesianCoordinateSystem>
> +              &lt;crs:dimension>2&lt;/crs:dimension>
> +              &lt;crs:CoordinateAxis>
> +                &lt;crs:axisDirection>north&lt;/crs:axisDirection>
> +                &lt;crs:AngularUnit>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>9108&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                &lt;/crs:AngularUnit>
> +              &lt;/crs:CoordinateAxis>
> +              &lt;crs:CoordinateAxis>
> +                &lt;crs:axisDirection>east&lt;/crs:axisDirection>
> +                &lt;crs:AngularUnit>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>9108&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                &lt;/crs:AngularUnit>
> +              &lt;/crs:CoordinateAxis>
> +            &lt;/crs:CartesianCoordinateSystem>
> +            &lt;crs:CoordinateReferenceSystem>
> +              &lt;!-- the reference system of that projected system is
> +                         WGS84 which is EPSG 4326 in EPSG codeSpace -->
> +              &lt;crs:NameSet>
> +                &lt;crs:name>WGS 84&lt;/crs:name>
> +              &lt;/crs:NameSet>
> +              &lt;crs:Identifier>
> +                &lt;crs:code>4326&lt;/crs:code>
> +                &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                &lt;crs:edition>5.2&lt;/crs:edition>
> +              &lt;/crs:Identifier>
> +            &lt;/crs:CoordinateReferenceSystem>
> +            &lt;crs:CoordinateTransformationDefinition>
> +              &lt;crs:sourceDimensions>2&lt;/crs:sourceDimensions>
> +              &lt;crs:targetDimensions>2&lt;/crs:targetDimensions>
> +              &lt;crs:ParameterizedTransformation>
> +                &lt;crs:TransformationMethod>
> +                  &lt;!-- the projection is a Mercator projection which is
> +                        EPSG 9805 in EPSG codeSpace -->
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>Mercator&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>9805&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:description>Mercator (2SP)&lt;/crs:description>
> +                &lt;/crs:TransformationMethod>
> +                &lt;crs:Parameter>
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>Latitude of 1st standart parallel&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>8823&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:value>0&lt;/crs:value>
> +                &lt;/crs:Parameter>
> +                &lt;crs:Parameter>
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>Longitude of natural origin&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>8802&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:value>0&lt;/crs:value>
> +                &lt;/crs:Parameter>
> +                &lt;crs:Parameter>
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>False Easting&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>8806&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:value>0&lt;/crs:value>
> +                &lt;/crs:Parameter>
> +                &lt;crs:Parameter>
> +                  &lt;crs:NameSet>
> +                    &lt;crs:name>False Northing&lt;/crs:name>
> +                  &lt;/crs:NameSet>
> +                  &lt;crs:Identifier>
> +                    &lt;crs:code>8807&lt;/crs:code>
> +                    &lt;crs:codeSpace>EPSG&lt;/crs:codeSpace>
> +                    &lt;crs:edition>5.2&lt;/crs:edition>
> +                  &lt;/crs:Identifier>
> +                  &lt;crs:value>0&lt;/crs:value>
> +                &lt;/crs:Parameter>
> +              &lt;/crs:ParameterizedTransformation>
> +            &lt;/crs:CoordinateTransformationDefinition>
> +          &lt;/crs:ProjectedCRS>
> +        &lt;/crs:CoordinateReferenceSystem>
> +      &lt;/rdf:Description>
> +    &lt;/rdf:RDF>
> +  &lt;/metadata>
> +
> +  &lt;!-- the actual map content -->
> +&lt;/svg>
> +</code></pre>
> +</div>
> +</main>
> +
> +  <h2 class="no-ref no-num heading settled" id="conformance"><span class="content">
> +Conformance</span><a class="self-link" href="#conformance"></a></h2>
> +
> +
> +  <h3 class="no-ref heading settled" id="conventions"><span class="content">
> +Document conventions</span><a class="self-link" href="#conventions"></a></h3>
> +
> +
> +  <p>Conformance requirements are expressed with a combination of
> +    descriptive assertions and RFC 2119 terminology. The key words "MUST",
> +    "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
> +    "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this
> +    document are to be interpreted as described in RFC 2119.
> +    However, for readability, these words do not appear in all uppercase
> +    letters in this specification.
> +
> +    </p>
> +  <p>All of the text of this specification is normative except sections
> +    explicitly marked as non-normative, examples, and notes. <a data-link-type="biblio" href="#biblio-rfc2119">[RFC2119]</a></p>
> +
> +
> +  <p>Examples in this specification are introduced with the words "for example"
> +    or are set apart from the normative text with <code>class="example"</code>,
> +    like this:
> +
> +    </p>
> +  <div class="example">
> +
> +   <p>This is an example of an informative example.</p>
> +
> +
> +  </div>
> +
> +
> +  <p>Informative notes begin with the word "Note" and are set apart from the
> +    normative text with <code>class="note"</code>, like this:
> +
> +    </p>
> +  <p class="note" role="note">Note, this is an informative note.</p>
> +
> +
> +  <p>Advisements are normative sections styled to evoke special attention and are
> +    set apart from other normative text with <code>&lt;strong class="advisement"></code>, like
> +    this:
> +
> +    <strong class="advisement">
> +        UAs MUST provide an accessible alternative.
> +    </strong>
> +
> +</p>
> +  <h3 class="no-ref heading settled" id="conformance-classes"><span class="content">
> +Conformance classes</span><a class="self-link" href="#conformance-classes"></a></h3>
> +
> +
> +  <p>Conformance to this specification
> +    is defined for three conformance classes:
> +    </p>
> +  <dl>
> +
> +   <dt>style sheet
> +
> +   <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#style-sheet">CSS
> +            style sheet</a>.
> +
> +   <dt>renderer
> +
> +   <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
> +            that interprets the semantics of a style sheet and renders
> +            documents that use them.
> +
> +   <dt>authoring tool
> +
> +   <dd>A <a href="http://www.w3.org/TR/CSS21/conform.html#user-agent">UA</a>
> +            that writes a style sheet.
> +
> +  </dl>
> +
> +
> +  <p>A style sheet is conformant to this specification
> +    if all of its statements that use syntax defined in this module are valid
> +    according to the generic CSS grammar and the individual grammars of each
> +    feature defined in this module.
> +
> +    </p>
> +  <p>A renderer is conformant to this specification
> +    if, in addition to interpreting the style sheet as defined by the
> +    appropriate specifications, it supports all the features defined
> +    by this specification by parsing them correctly
> +    and rendering the document accordingly. However, the inability of a
> +    UA to correctly render a document due to limitations of the device
> +    does not make the UA non-conformant. (For example, a UA is not
> +    required to render color on a monochrome monitor.)
> +
> +    </p>
> +  <p>An authoring tool is conformant to this specification
> +    if it writes style sheets that are syntactically correct according to the
> +    generic CSS grammar and the individual grammars of each feature in
> +    this module, and meet all other conformance requirements of style sheets
> +    as described in this module.
> +
> +</p>
> +  <h3 class="no-ref heading settled" id="partial"><span class="content">
> +Partial implementations</span><a class="self-link" href="#partial"></a></h3>
> +
> +
> +  <p>So that authors can exploit the forward-compatible parsing rules to
> +    assign fallback values, CSS renderers <strong>must</strong>
> +    treat as invalid (and <a href="http://www.w3.org/TR/CSS21/conform.html#ignore">ignore
> +    as appropriate</a>) any at-rules, properties, property values, keywords,
> +    and other syntactic constructs for which they have no usable level of
> +    support. In particular, user agents <strong>must not</strong> selectively
> +    ignore unsupported component values and honor supported values in a single
> +    multi-value property declaration: if any value is considered invalid
> +    (as unsupported values must be), CSS requires that the entire declaration
> +    be ignored.</p>
> +
> +
> +  <h3 class="no-ref heading settled" id="experimental"><span class="content">
> +Experimental implementations</span><a class="self-link" href="#experimental"></a></h3>
> +
> +
> +  <p>To avoid clashes with future CSS features, the CSS2.1 specification
> +    reserves a <a href="http://www.w3.org/TR/CSS21/syndata.html#vendor-keywords">prefixed
> +    syntax</a> for proprietary and experimental extensions to CSS.
> +
> +    </p>
> +  <p>Prior to a specification reaching the Candidate Recommendation stage
> +    in the W3C process, all implementations of a CSS feature are considered
> +    experimental. The CSS Working Group recommends that implementations
> +    use a vendor-prefixed syntax for such features, including those in
> +    W3C Working Drafts. This avoids incompatibilities with future changes
> +    in the draft.
> +    </p>
> +
> +
> +  <h3 class="no-ref heading settled" id="testing"><span class="content">
> +Non-experimental implementations</span><a class="self-link" href="#testing"></a></h3>
> +
> +
> +  <p>Once a specification reaches the Candidate Recommendation stage,
> +    non-experimental implementations are possible, and implementors should
> +    release an unprefixed implementation of any CR-level feature they
> +    can demonstrate to be correctly implemented according to spec.
> +
> +    </p>
> +  <p>To establish and maintain the interoperability of CSS across
> +    implementations, the CSS Working Group requests that non-experimental
> +    CSS renderers submit an implementation report (and, if necessary, the
> +    testcases used for that implementation report) to the W3C before
> +    releasing an unprefixed implementation of any CSS features. Testcases
> +    submitted to W3C are subject to review and correction by the CSS
> +    Working Group.
> +
> +    </p>
> +  <p>Further information on submitting testcases and implementation reports
> +    can be found from on the CSS Working Group’s website at
> +    <a href="http://www.w3.org/Style/CSS/Test/">http://www.w3.org/Style/CSS/Test/</a>.
> +    Questions should be directed to the
> +    <a href="http://lists.w3.org/Archives/Public/public-css-testsuite">public-css-testsuite@w3.org</a>
> +    mailing list.
> +
> +
> +
> +</p>
> +  <h2 class="no-num heading settled" id="references"><span class="content">References</span><a class="self-link" href="#references"></a></h2>
> +  <h3 class="no-num heading settled" id="normative"><span class="content">Normative References</span><a class="self-link" href="#normative"></a></h3>
> +  <dl>
> +   <dt id="biblio-rfc2119"><a class="self-link" href="#biblio-rfc2119"></a>[rfc2119]
> +   <dd>S. Bradner. <a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>. March 1997. Best Current Practice. URL: <a href="https://tools.ietf.org/html/rfc2119">https://tools.ietf.org/html/rfc2119</a>
> +  </dl>
> +  <h3 class="no-num heading settled" id="informative"><span class="content">Informative References</span><a class="self-link" href="#informative"></a></h3>
> +  <dl>
> +   <dt id="biblio-rdf-primer"><a class="self-link" href="#biblio-rdf-primer"></a>[rdf-primer]
> +   <dd>Frank Manola; Eric Miller. <a href="http://www.w3.org/TR/rdf-primer/">RDF Primer</a>. 10 February 2004. REC. URL: <a href="http://www.w3.org/TR/rdf-primer/">http://www.w3.org/TR/rdf-primer/</a>
> +  </dl>
> +  <h2 class="no-num heading settled" id="index"><span class="content">Index</span><a class="self-link" href="#index"></a></h2>
> +  <ul class="indexlist">
> +   <li>svg:transform, <a href="#svgtransform">2</a>
> +  </ul></body>
> +</html>
> \ No newline at end of file
>
>
> ============================================================
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Received on Wednesday, 25 February 2015 16:52:10 UTC

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