Better definition for class attribute.

Author: fantasai

selectors4/Overview.html

@@ -1560,25 +1560,17 @@ <h3 id=def-values><span class=secno>6.4. </span> Default attribute values
 
   <h3 id=class-html><span class=secno>6.5. </span> Class selectors</h3>
 
-  <p>Working with HTML, authors may use the "period" notation (also known as
-   "full stop", U+002E, <code>.</code>) as an alternative to the
-   <code>~=</code> notation when representing the <code>class</code>
-   attribute. Thus, for HTML, <code>div.value</code> and
-   <code>div[class~=value]</code> have the same meaning. The attribute value
-   must immediately follow the full stop (<code>.</code>).
-
-  <p>UAs may apply selectors using the period (.) notation in XML documents
-   if the UA has namespace-specific knowledge that allows it to determine
-   which attribute is the "class" attribute for the respective namespace. One
-   such example of namespace-specific knowledge is the prose in the
-   specification for a particular namespace (e.g. SVG 1.0 <a href="#SVG11"
-   rel=biblioentry>[SVG11]<!--{{SVG11}}--></a> describes the <a
-   href="http://www.w3.org/TR/2001/PR-SVG-20010719/styling.html#ClassAttribute">SVG
-   <code>class</code> attribute</a> and how a UA should interpret it, and
-   similarly MathML 1.01 <a href="#MATHML"
-   rel=biblioentry>[MATHML]<!--{{MATHML}}--></a> describes the <a
-   href="http://www.w3.org/1999/07/REC-MathML-19990707/chapter2.html#sec2.3.4">MathML
-   <code>class</code> attribute</a>.)
+  <p>The class selector is given as a full stop (. U+002E) immediately
+   followed by an identifier. It represents an element belonging to the class
+   identified by the identifier, as defined by the document language. For
+   example, in <a href="#HTML5" rel=biblioentry>[HTML5]<!--{{HTML5}}--></a>,
+   <a href="#SVG11" rel=biblioentry>[SVG11]<!--{{SVG11}}--></a>, and <a
+   href="#MATHML" rel=biblioentry>[MATHML]<!--{{MATHML}}--></a> membership in
+   a class is given by the <code>class</code> attribute: in these languages
+   it is equivalent to the <code>~=</code> notation applied to the local
+   <code>class</code> attribute (i.e.
+   <code>[class~=<var>identifier</var>]</code>), except that it has a higher
+   <a href="#specificity">specificity</a>.
 
   <div class=example>
    <p>CSS examples:</p>

selectors4/Overview.src.html

@@ -1080,25 +1080,15 @@ <h3 id=def-values>
 <h3 id=class-html>
 Class selectors</h3>
 
-  <p>Working with HTML, authors may use the "period" notation (also
-  known as "full stop", U+002E, <code>.</code>) as an alternative to the
-  <code>~=</code> notation when representing the <code>class</code>
-  attribute. Thus, for HTML, <code>div.value</code> and
-  <code>div[class~=value]</code> have the same meaning. The attribute
-  value must immediately follow the full stop
-  (<code>.</code>).</p>
-
-  <p>UAs may apply selectors using the period (.) notation in XML
-  documents if the UA has namespace-specific knowledge that allows it to
-  determine which attribute is the "class" attribute for the
-  respective namespace. One such example of namespace-specific knowledge
-  is the prose in the specification for a particular namespace (e.g. SVG
-  1.0 [[SVG11]] describes the <a
-  href="http://www.w3.org/TR/2001/PR-SVG-20010719/styling.html#ClassAttribute">SVG
-  <code>class</code> attribute</a> and how a UA should interpret it, and
-  similarly MathML 1.01 [[MATHML]] describes the <a
-  href="http://www.w3.org/1999/07/REC-MathML-19990707/chapter2.html#sec2.3.4">MathML
-  <code>class</code> attribute</a>.)</p>
+  <p>The class selector is given as a full stop (. U+002E) immediately
+  followed by an identifier. It represents an element belonging to the
+  class identified by the identifier, as defined by the document language.
+  For example, in [[HTML5]], [[SVG11]], and [[MATHML]] membership in a
+  class is given by the <code>class</code> attribute: in these languages
+  it is equivalent to the <code>~=</code> notation applied to the
+  local <code>class</code> attribute
+  (i.e. <code>[class~=<var>identifier</var>]</code>),
+  except that it has a higher <a href="#specificity">specificity</a>.
 
   <div class="example">
    <p>CSS examples:</p>