W3C home > Mailing lists > Public > public-html-diffs@w3.org > December 2008

spec/Overview.html 1.1718 2547 * Header cells can now themselves have h

From: poot <cvsmail@w3.org>
Date: Sat, 20 Dec 2008 18:24:38 +0900 (JST)
To: public-html-diffs@w3.org
Message-Id: <20081220092439.010F12BC75@toro.w3.mag.keio.ac.jp>

* Header cells can now themselves have headers.  * Reversed the way the
header association algorithm is presented, such   that it starts from a
cell and reports the headers rather than   generating the list of
headers for each cell on a header-by-header   basis.  * Made it so that
if headers="" points to a <td> element, the   association is now set up,
despite being non-conforming.  * Header cells that are automatically
associating now no longer stop   associating when they hit equivalent
cells until they have also hit   a data cell.  * The "col" and "row"
scope values now act like the implied auto value   except that they
force the direction.  * Empty header cells no longer get automatically
associated.  * Removed the wide header cell heuristic.  * Made
headers="" use the same ID discovery mechanism as   getElementById()
(namely, first match), to avoid implementations   having to support
multiple such mechanisms.  * Made the spec define if a header is a
column header or a row header   in the case where scope="" is omitted.
* Made scope=rowgroup and scope=colgroup non-conforming when not in an
appropriate group. (whatwg r2547)

scope
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#dom-th-scope
rowSpan
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#dom-tdth-rowspan
cellIndex
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#dom-tdth-cellindex
column header
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#column-header
column
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#concept-column
4.9.12 Attributes common to td and th elements
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#attributes-common-to-td-and-th-elements
internal algorithm for scanning and assigning header cells
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#internal-algorithm-for-scanning-and-assigning-header-cells
headers
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#attr-tdth-headers
4.10 Forms
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#forms
rowspan
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#attr-tdth-rowspan
row
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#attr-th-scope-row
algorithm for growing downward-growing cells
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#algorithm-for-growing-downward-growing-cells
auto
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#attr-th-scope-auto
row header
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#row-header
rowgroup
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#attr-th-scope-rowgroup
colgroup
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#attr-th-scope-colgroup
HTMLTableCellElement
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#htmltablecellelement
colSpan
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#dom-tdth-colspan
algorithm for processing rows
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#algorithm-for-processing-rows
HTMLTableDataCellElement
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#htmltabledatacellelement
4.9.13.2 Forming relationships between data cells and header cells
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#header-and-data-cell-semantics
algorithm for assigning header cells
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#algorithm-for-assigning-header-cells
row group header
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#row-group-header
headers
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#dom-tdth-headers
empty cell
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#empty-cell
column group header
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#column-group-header
Status of this document
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#status-of-this-document
row
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#concept-row
cell
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#concept-cell
A vocabulary and associated APIs for HTML and XHTML
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#a-vocabulary-and-associated-apis-for-html-and-xhtml
col
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#attr-th-scope-col
4.9.11 The th element
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#the-th-element
Editor's Draft 20 December 2008
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#editor-s-draft-date-zzz-9-june-2008
4.9.10 The td element
http://people.w3.org/mike/diffs/html5/spec/Overview.1.1718.html#the-td-element

http://people.w3.org/mike/diffs/html5/spec/Overview.diff.html
http://dev.w3.org/cvsweb/html5/spec/Overview.html?r1=1.1717&r2=1.1718&f=h
http://html5.org/tools/web-apps-tracker?from=2546&to=2547

===================================================================
RCS file: /sources/public/html5/spec/Overview.html,v
retrieving revision 1.1717
retrieving revision 1.1718
diff -u -d -r1.1717 -r1.1718
--- Overview.html	19 Dec 2008 06:39:01 -0000	1.1717
+++ Overview.html	20 Dec 2008 09:21:48 -0000	1.1718
@@ -8,7 +8,7 @@
    <p><a href=http://www.w3.org/><img alt=W3C height=48 src=http://www.w3.org/Icons/w3c_home width=72></a></p>
    <h1>HTML 5</h1>
    <h2 class="no-num no-toc" id=a-vocabulary-and-associated-apis-for-html-and-xhtml>A vocabulary and associated APIs for HTML and XHTML</h2>
-   <h2 class="no-num no-toc" id=editor-s-draft-date-zzz-9-june-2008><!-- "W3C Working Draft" --> Editor's Draft <!--ZZZ-->19 December 2008</h2>
+   <h2 class="no-num no-toc" id=editor-s-draft-date-zzz-9-june-2008><!-- "W3C Working Draft" --> Editor's Draft <!--ZZZ-->20 December 2008</h2>
    <dl><!-- ZZZ: update the month/day
     <dt>This Version:</dt>
     <dd><a href="http://www.w3.org/TR/2008/WD-html5-20080610/">http://www.w3.org/TR/2008/WD-html5-20080610/</a></dd>
@@ -97,7 +97,7 @@
   specification's progress along the W3C Recommendation
   track.
   <!--ZZZ:-->
-  This specification is the 19 December 2008 <!--ZZZ "Working Draft"-->Editor's Draft.
+  This specification is the 20 December 2008 <!--ZZZ "Working Draft"-->Editor's Draft.
   <!--:ZZZ-->
   </p><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- relationship to other work (required) --><p>This specification is also being produced by the <a href=http://www.whatwg.org/>WHATWG</a>. The two specifications are
   identical from the table of contents onwards.</p><!-- UNDER NO CIRCUMSTANCES IS THE FOLLOWING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- UNDER NO CIRCUMSTANCES IS THE PRECEDING PARAGRAPH TO BE REMOVED OR EDITED WITHOUT TALKING TO IAN FIRST --><!-- context and rationale (required) --><p>This specification is intended to replace (be a new version of)
@@ -17954,28 +17954,14 @@
    <dt>Element-specific attributes:</dt>
    <dd><code title=attr-tdth-colspan><a href=#attr-tdth-colspan>colspan</a></code></dd>
    <dd><code title=attr-tdth-rowspan><a href=#attr-tdth-rowspan>rowspan</a></code></dd>
-   <dd><code title=attr-td-headers><a href=#attr-td-headers>headers</a></code></dd>
-   <!-- XXXv2 char, to specify the decimal character used in numeric cells -->
+   <dd><code title=attr-tdth-headers><a href=#attr-tdth-headers>headers</a></code></dd>
+   <!-- v2 char, to specify the decimal character used in numeric cells -->
    <dt>DOM interface:</dt>
    <dd>
-    <pre class=idl>interface <dfn id=htmltabledatacellelement>HTMLTableDataCellElement</dfn> : <a href=#htmltablecellelement>HTMLTableCellElement</a> {
-           attribute DOMString <a href=#dom-td-headers title=dom-td-headers>headers</a>;
-};</pre>
+    <pre class=idl>interface <dfn id=htmltabledatacellelement>HTMLTableDataCellElement</dfn> : <a href=#htmltablecellelement>HTMLTableCellElement</a> {};</pre>
    </dd>
-  </dl><p>The <code><a href=#the-td-element>td</a></code> element represents a data <a href=#concept-cell title=concept-cell>cell</a> in a table.<p>The <code><a href=#the-td-element>td</a></code> element may have a <dfn id=attr-td-headers title=attr-td-headers><code>headers</code></dfn> content attribute
-  specified. The <code title=attr-td-headers><a href=#attr-td-headers>headers</a></code>
-  attribute, if specified, must contain a string consisting of an
-  <a href=#unordered-set-of-unique-space-separated-tokens>unordered set of unique space-separated tokens</a>, each of
-  which must have the value of an ID of a <code><a href=#the-th-element>th</a></code> element
-  taking part in the same <a href=#concept-table title=concept-table>table</a> as
-  the <code><a href=#the-td-element>td</a></code> element (as defined by the <a href=#table-model>table
-  model</a>).<p>The exact effect of the attribute is described in detail in the
-  <a href=#algorithm-for-assigning-header-cells-to-data-cells>algorithm for assigning header cells to data cells</a>,
-  which user agents must apply to determine the relationships between
-  data cells and header cells.<p>The <code><a href=#the-td-element>td</a></code> element and its <code title=attr-tdth-colspan><a href=#attr-tdth-colspan>colspan</a></code> and <code title=attr-tdth-rowspan><a href=#attr-tdth-rowspan>rowspan</a></code> attributes take part in the
-  <a href=#table-model>table model</a>.<p>The <dfn id=dom-td-headers title=dom-td-headers><code>headers</code></dfn> DOM
-  attribute must <a href=#reflect>reflect</a> the content attribute of the
-  same name.<h4 id=the-th-element><span class=secno>4.9.11 </span>The <dfn><code>th</code></dfn> element</h4><dl class=element><dt>Categories</dt>
+  </dl><p>The <code><a href=#the-td-element>td</a></code> element represents a data <a href=#concept-cell title=concept-cell>cell</a> in a table.<p class=note>The <code><a href=#the-td-element>td</a></code> element and its <code title=attr-tdth-colspan><a href=#attr-tdth-colspan>colspan</a></code>, <code title=attr-tdth-rowspan><a href=#attr-tdth-rowspan>rowspan</a></code>, and <code title=attr-tdth-headers><a href=#attr-tdth-headers>headers</a></code> attributes take part in the
+  <a href=#table-model>table model</a>.<h4 id=the-th-element><span class=secno>4.9.11 </span>The <dfn><code>th</code></dfn> element</h4><dl class=element><dt>Categories</dt>
    <dd>None.</dd>
    <dt>Contexts in which this element may be used:</dt>
    <dd>As a child of a <code><a href=#the-tr-element>tr</a></code> element.</dd>
@@ -17984,6 +17970,7 @@
    <dt>Element-specific attributes:</dt>
    <dd><code title=attr-tdth-colspan><a href=#attr-tdth-colspan>colspan</a></code></dd>
    <dd><code title=attr-tdth-rowspan><a href=#attr-tdth-rowspan>rowspan</a></code></dd>
+   <dd><code title=attr-tdth-headers><a href=#attr-tdth-headers>headers</a></code></dd>
    <dd><code title=attr-th-scope><a href=#attr-th-scope>scope</a></code></dd>
    <dt>DOM interface:</dt>
    <dd>
@@ -17997,37 +17984,40 @@
   have explicit keywords:<dl><dt>The <dfn id=attr-th-scope-row title=attr-th-scope-row><code>row</code></dfn>
    keyword, which maps to the <i>row</i> state</dt>
 
-   <dd>The <i>row</i> state means the header cell applies to all the
-   remaining cells in the row.</dd>
+   <dd>The <i>row</i> state means the header cell applies to some of
+   the subsequent cells in the same row(s).</dd>
 
    <dt>The <dfn id=attr-th-scope-col title=attr-th-scope-col><code>col</code></dfn>
    keyword, which maps to the <i>column</i> state</dt>
 
-   <dd>The <i>column</i> state means the header cell applies to all
-   the remaining cells in the column.</dd>
+   <dd>The <i>column</i> state means the header cell applies to some
+   of the subsequent cells in the same column(s).</dd>
 
    <dt>The <dfn id=attr-th-scope-rowgroup title=attr-th-scope-rowgroup><code>rowgroup</code></dfn> keyword,
    which maps to the <i>row group</i> state</dt>
 
-   <dd>The <i>row group</i> state means the header cell applies to
-   all the remaining cells in the row group.</dd>
+   <dd>The <i>row group</i> state means the header cell applies to all
+   the remaining cells in the row group. A <code><a href=#the-th-element>th</a></code> element's
+   <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attribute must not be in
+   the <a href=#attr-th-scope-rowgroup title=attr-th-scope-rowgroup>row group</a> state if
+   the element is not anchored in a <a href=#concept-row-group title=concept-row-group>row group</a>.</dd>
 
    <dt>The <dfn id=attr-th-scope-colgroup title=attr-th-scope-colgroup><code>colgroup</code></dfn> keyword,
    which maps to the <i>column group</i> state</dt>
 
-   <dd>The <i>column group</i> state means the header cell applies
-   to all the remaining cells in the column group.</dd>
+   <dd>The <i>column group</i> state means the header cell applies to
+   all the remaining cells in the column group. A <code><a href=#the-th-element>th</a></code>
+   element's <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attribute must
+   not be in the <a href=#attr-th-scope-colgroup title=attr-th-scope-colgroup>column
+   group</a> state if the element is not anchored in a <a href=#concept-column-group title=concept-column-group>column group</a>.</dd>
 
-   <dt>The <i>auto</i> state</dt>
+   <dt>The <dfn id=attr-th-scope-auto title=attr-th-scope-auto>auto</dfn> state</dt>
 
    <dd>The <i>auto</i> state makes the header cell apply to a set of
    cells selected based on context.</dd>
 
   </dl><p>The <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attribute's
-  <i>missing value default</i> is the <i>auto</i> state.<p>The exact effect of these values is described in detail in the
-  <a href=#algorithm-for-assigning-header-cells-to-data-cells>algorithm for assigning header cells to data cells</a>,
-  which user agents must apply to determine the relationships between
-  data cells and header cells.<p>The <code><a href=#the-th-element>th</a></code> element and its <code title=attr-tdth-colspan><a href=#attr-tdth-colspan>colspan</a></code> and <code title=attr-tdth-rowspan><a href=#attr-tdth-rowspan>rowspan</a></code> attributes take part in the
+  <i>missing value default</i> is the <i>auto</i> state.<p class=note>The <code><a href=#the-th-element>th</a></code> element and its <code title=attr-tdth-colspan><a href=#attr-tdth-colspan>colspan</a></code>, <code title=attr-tdth-rowspan><a href=#attr-tdth-rowspan>rowspan</a></code>, <code title=attr-tdth-headers><a href=#attr-tdth-headers>headers</a></code>, and <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attributes take part in the
   <a href=#table-model>table model</a>.<p>The <dfn id=dom-th-scope title=dom-th-scope><code>scope</code></dfn> DOM
   attribute must <a href=#reflect>reflect</a> the content attribute of the
   same name.<h4 id=attributes-common-to-td-and-th-elements><span class=secno>4.9.12 </span>Attributes common to <code><a href=#the-td-element>td</a></code> and <code><a href=#the-th-element>th</a></code> elements</h4><p>The <code><a href=#the-td-element>td</a></code> and <code><a href=#the-th-element>th</a></code> elements may have a <dfn id=attr-tdth-colspan title=attr-tdth-colspan><code>colspan</code></dfn> content
@@ -18035,11 +18025,20 @@
   integer</a> greater than zero.<p>The <code><a href=#the-td-element>td</a></code> and <code><a href=#the-th-element>th</a></code> elements may also have a
   <dfn id=attr-tdth-rowspan title=attr-tdth-rowspan><code>rowspan</code></dfn> content
   attribute specified, whose value must be a <a href=#valid-non-negative-integer>valid non-negative
-  integer</a>.<p>The <code><a href=#the-td-element>td</a></code> and <code><a href=#the-th-element>th</a></code> elements implement
+  integer</a>.<p>The <code><a href=#the-td-element>td</a></code> and <code><a href=#the-th-element>th</a></code> element may have a <dfn id=attr-tdth-headers title=attr-tdth-headers><code>headers</code></dfn> content
+  attribute specified. The <code title=attr-tdth-headers><a href=#attr-tdth-headers>headers</a></code> attribute, if specified,
+  must contain a string consisting of an <a href=#unordered-set-of-unique-space-separated-tokens>unordered set of unique
+  space-separated tokens</a>, each of which must have the value of
+  an ID of a <code><a href=#the-th-element>th</a></code> element taking part in the same <a href=#concept-table title=concept-table>table</a> as the <code><a href=#the-td-element>td</a></code> or
+  <code><a href=#the-th-element>th</a></code> element (as defined by the <a href=#table-model>table
+  model</a>).<p class=note>The <code title=attr-tdth-colspan><a href=#attr-tdth-colspan>colspan</a></code>,
+  <code title=attr-tdth-rowspan><a href=#attr-tdth-rowspan>rowspan</a></code>, and <code title=attr-tdth-headers><a href=#attr-tdth-headers>headers</a></code> attributes take part in the
+  <a href=#table-model>table model</a>.<p>The <code><a href=#the-td-element>td</a></code> and <code><a href=#the-th-element>th</a></code> elements implement
   interfaces that inherit from the <code><a href=#htmltablecellelement>HTMLTableCellElement</a></code>
   interface:<pre class=idl>interface <dfn id=htmltablecellelement>HTMLTableCellElement</dfn> : <a href=#htmlelement>HTMLElement</a> {
            attribute long <a href=#dom-tdth-colspan title=dom-tdth-colSpan>colSpan</a>;
            attribute long <a href=#dom-tdth-rowspan title=dom-tdth-rowSpan>rowSpan</a>;
+           attribute DOMString <a href=#dom-tdth-headers title=dom-tdth-headers>headers</a>;
   readonly attribute long <a href=#dom-tdth-cellindex title=dom-tdth-cellIndex>cellIndex</a>;
 };</pre><p>The <dfn id=dom-tdth-colspan title=dom-tdth-colSpan><code>colSpan</code></dfn> DOM
   attribute must <a href=#reflect>reflect</a> the content attribute of the
@@ -18048,7 +18047,9 @@
   attribute must <a href=#reflect>reflect</a> the content attribute of the
   same name. Its default value, which must be used if <a href=#rules-for-parsing-non-negative-integers title="rules for parsing non-negative integers">parsing the
   attribute as a non-negative integer</a> returns an error, is also
-  1.<p>The <dfn id=dom-tdth-cellindex title=dom-tdth-cellIndex><code>cellIndex</code></dfn>
+  1.<p>The <dfn id=dom-tdth-headers title=dom-tdth-headers><code>headers</code></dfn> DOM
+  attribute must <a href=#reflect>reflect</a> the content attribute of the
+  same name.<p>The <dfn id=dom-tdth-cellindex title=dom-tdth-cellIndex><code>cellIndex</code></dfn>
   DOM attribute must, if the element has a parent <code><a href=#the-tr-element>tr</a></code>
   element, return the index of the cell's element in the parent
   element's <code title=dom-tr-cells><a href=#dom-tr-cells>cells</a></code> collection. If
@@ -18066,9 +18067,10 @@
   the cell covers all the slots with coordinates (<var title="">x</var>, <var title="">y</var>) where <span><var title="">cell<sub title="">x</sub></var>&nbsp;&le;&nbsp;<var title="">x</var>&nbsp;&lt;&nbsp;<var title="">cell<sub title="">x</sub></var>+<var title="">width</var></span> and
   <span><var title="">cell<sub title="">y</sub></var>&nbsp;&le;&nbsp;<var title="">y</var>&nbsp;&lt;&nbsp;<var title="">cell<sub title="">y</sub></var>+<var title="">height</var></span>. Cells can
   either be <em>data cells</em> or <em>header cells</em>. Data cells
-  correspond to <code><a href=#the-td-element>td</a></code> elements, and have zero or more
-  associated header cells. Header cells correspond to <code><a href=#the-th-element>th</a></code>
-  elements.<p>A <dfn id=concept-row title=concept-row>row</dfn> is a complete set of slots
+  correspond to <code><a href=#the-td-element>td</a></code> elements, and header cells correspond
+  to <code><a href=#the-th-element>th</a></code> elements. Cells of both types can have zero or
+  more associated header cells.<p>It is possible, in certain error cases, for two cells to occupy
+  the same slot.<p>A <dfn id=concept-row title=concept-row>row</dfn> is a complete set of slots
   from <span><var title="">x</var>=0</span> to <span><var title="">x</var>=<var title="">x<sub title="">width</sub></var>-1</span>, for a particular value of <var title="">y</var>. Rows correspond to <code><a href=#the-tr-element>tr</a></code> elements.<p>A <dfn id=concept-column title=concept-column>column</dfn> is a complete set of
   slots from <span><var title="">y</var>=0</span> to <span><var title="">y</var>=<var title="">y<sub title="">height</sub></var>-1</span>, for a particular value of <var title="">x</var>. Columns can correspond to <code><a href=#the-col-element>col</a></code>
   elements, but in the absence of <code><a href=#the-col-element>col</a></code> elements are
@@ -18606,10 +18608,10 @@
 
     <p>If the <var title="">current cell</var> element is a
     <code><a href=#the-th-element>th</a></code> element, let this new cell <var title="">c</var>
-    be a header cell; otherwise, let it be a data cell. To establish
-    what header cells apply to a data cell, use the <a href=#algorithm-for-assigning-header-cells-to-data-cells>algorithm
-    for assigning header cells to data cells</a> described in the
-    next section.</p>
+    be a header cell; otherwise, let it be a data cell.</p>
+
+    <p>To establish which header cells apply to the <var title="">current cell</var> element, use the <a href=#algorithm-for-assigning-header-cells>algorithm for
+    assigning header cells</a> described in the next section.</p>
 
     <p>If any of the slots involved already had a <a href=#concept-cell title=concept-cell>cell</a> covering them, then this is a
     <a href=#table-model-error>table model error</a>. Those slots now have two cells
@@ -18660,279 +18662,326 @@
   agent must, for each {<var title="">cell</var>, <var title="">cell<sub title="">x</sub></var>, <var title="">width</var>}
   tuple in the <var title="">list of downward-growing cells</var>, if
   any, extend the <a href=#concept-cell title=concept-cell>cell</a> <var title="">cell</var> so that it also covers the slots with
-  coordinates (<var title="">x</var>, <var title="">y<sub title="">current</sub></var>), where <span><var title="">cell<sub title="">x</sub></var>&nbsp;&le;&nbsp;<var title="">x</var>&nbsp;&lt;&nbsp;<var title="">cell<sub title="">x</sub></var>+<var title="">width</var></span>.<h5 id=header-and-data-cell-semantics><span class=secno>4.9.13.2 </span>Forming relationships between data cells and header cells</h5><p>Each data cell can be assigned zero or more header cells. The
-  <dfn id=algorithm-for-assigning-header-cells-to-data-cells>algorithm for assigning header cells to data cells</dfn> is as
-  follows.<ol><li>
+  coordinates (<var title="">x</var>, <var title="">y<sub title="">current</sub></var>), where <span><var title="">cell<sub title="">x</sub></var>&nbsp;&le;&nbsp;<var title="">x</var>&nbsp;&lt;&nbsp;<var title="">cell<sub title="">x</sub></var>+<var title="">width</var></span>.<h5 id=header-and-data-cell-semantics><span class=secno>4.9.13.2 </span>Forming relationships between data cells and header cells</h5><p>Each cell can be assigned zero or more header cells. The
+  <dfn id=algorithm-for-assigning-header-cells>algorithm for assigning header cells</dfn> to a cell <var title="">principal cell</var> is as follows.<ol><!-- INITIALIZATION --><li>
 
-    <p>For each header cell in the table, in <a href=#tree-order>tree order</a>,
-    run these substeps:</p>
+    <p>Let <var title="">header list</var> be an empty list of
+    cells.</p>
 
-    <ol><li>
+   </li>
 
-      <p>Let (<var title="">header<sub title="">x</sub></var>, <var title="">header<sub title="">y</sub></var>) be the coordinate of
-      the slot to which the header cell is anchored.</p>
+   <li>
 
-     </li>
+    <p>Let (<var title="">principal<sub title="">x</sub></var>, <var title="">principal<sub title="">y</sub></var>) be the coordinate
+    of the slot to which the <var title="">principal cell</var> is
+    anchored.</p>
 
-     <li>
+   </li>
 
-      <p>Let <var title="">header<sub title="">width</sub></var> be
-      the width of the header cell.</p>
+   <li>
 
-     </li>
+    <dl class=switch><dt>If the <var title="">principal cell</var> has a <code title=attr-tdth-headers><a href=#attr-tdth-headers>headers</a></code> attribute specified</dt>
 
-     <li>
+     <dd>
 
-      <p>Let <var title="">header<sub title="">height</sub></var> be
-      the height of the header cell.</p>
+      <!-- HEADERS="" -->
 
-     </li>
+      <ol><li>
 
-     <li>
+        <p>Take the value of the <var title="">principal cell</var>'s
+        <code title=attr-tdth-headers><a href=#attr-tdth-headers>headers</a></code> attribute and
+        <a href=#split-a-string-on-spaces title="split a string on spaces">split it on
+        spaces</a>, letting <var title="">id list</var> be the list
+        of tokens obtained.</p>
 
-      <p>Let <var title="">data cells</var> be a list of data cells,
-      initially empty.</p>
+       </li>
 
-     </li>
+       <li>
 
-     <li>
+        <!-- support headers="" to <td> for legacy compat -->
+        <!-- note that it's not conforming though -->
+        <p>For each token in the <var title="">id list</var>, if the
+        first element in the <code>Document</code> with an ID equal to
+        the token is a cell in the same <a href=#concept-table title=concept-table>table</a>, and that cell is not the
+        <var title="">principal cell</var>, then add that cell to <var title="">header list</var>.</p>
 
-      <p>Examine the <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code>
-      attribute of the <code><a href=#the-th-element>th</a></code> element corresponding to the
-      header cell, and, based on its state, apply the appropriate
-      substep:</p>
+       </li>
 
-      <dl class=switch><dt>If it is in the <i title=attr-th-scope-row><a href=#attr-th-scope-row>row</a></i> state</dt>
+      </ol></dd>
 
-       <dd>
 
-        <p>Add all the data cells that cover slots with coordinates
-        (<var title="">slot<sub title="">x</sub></var>, <var title="">slot<sub title="">y</sub></var>), where <span><var title="">header<sub title="">x</sub></var>+<var title="">header<sub title="">width</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">x</sub></var>&nbsp;&lt;&nbsp;<var title="">x<sub title="">width</sub></var></span> and
-        <span><var title="">header<sub title="">y</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">y</sub></var>&nbsp;&lt;&nbsp;<var title="">header<sub title="">y</sub></var>+<var title="">header<sub title="">height</sub></var></span>, to the <var title="">data
-        cells</var> list.</p>
+     <dt>If <var title="">principal cell</var> does not have a <code title=attr-tdth-headers><a href=#attr-tdth-headers>headers</a></code> attribute specified</dt>
 
-       </dd>
+     <dd>
 
-       <dt>If it is in the <i title=attr-th-scope-col><a href=#attr-th-scope-col>column</a></i> state</dt>
+      <ol><li>
 
-       <dd>
+        <p>Let <var title="">principal<sub title="">width</sub></var>
+        be the width of the <var title="">principal cell</var>.</p>
 
-        <p>Add all the data cells that cover slots with coordinates
-        (<var title="">slot<sub title="">x</sub></var>, <var title="">slot<sub title="">y</sub></var>), where <span><var title="">header<sub title="">x</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">x</sub></var>&nbsp;&lt;&nbsp;<var title="">header<sub title="">x</sub></var>+<var title="">header<sub title="">width</sub></var></span> and
-        <span><var title="">header<sub title="">y</sub></var>+<var title="">header<sub title="">height</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">y</sub></var>&nbsp;&lt;&nbsp;<var title="">y<sub title="">height</sub></var></span>, to the <var title="">data cells</var> list.</p>
+       </li>
 
-       </dd>
+       <li>
 
-       <dt>If it is in the <i title=attr-th-scope-rowgroup><a href=#attr-th-scope-rowgroup>row group</a></i> state</dt>
+        <p>Let <var title="">principal<sub title="">height</sub></var>
+        be the height of the <var title="">principal cell</var>.</p>
 
-       <dd>
+       </li>
 
-        <p>If the header cell is not in a <a href=#concept-row-group title=concept-row-group>row group</a>, then do
-        nothing.</p>
 
-        <p>Otherwise, let (0, <var title="">group<sub title="">y</sub></var>) be the slot at which the row group is
-        anchored, let <var title="">height</var> be the number of rows
-        in the row group, and add all the data cells that cover slots
-        with coordinates (<var title="">slot<sub title="">x</sub></var>, <var title="">slot<sub title="">y</sub></var>), where <span><var title="">header<sub title="">x</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">x</sub></var>&nbsp;&lt;&nbsp;<var title="">x<sub title="">width</sub></var></span> and <span><var title="">header<sub title="">y</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">y</sub></var>&nbsp;&lt;&nbsp;<var title="">group<sub title="">y</sub></var>+<var title="">height</var></span>, to the <var title="">data
-        cells</var> list.</p>
+       <!-- HORIZONTAL -->
 
-       </dd>
+       <li>
 
-       <dt>If it is in the <i title=attr-th-scope-colgroup><a href=#attr-th-scope-colgroup>column group</a></i> state</dt>
+        <p>For each value of <var title="">y</var> from <var title="">principal<sub title="">y</sub></var> to <span><var title="">principal<sub title="">y</sub></var>+<var title="">principal<sub title="">height</sub></var>-1</span>,
+        run the <a href=#internal-algorithm-for-scanning-and-assigning-header-cells>internal algorithm for scanning and assigning
+        header cells</a>, with the <var title="">principal
+        cell</var>, the <var title="">header list</var>, the initial
+        coordinate (<var title="">principal<sub title="">x</sub></var>,<var title="">y</var>), and the
+        increments <span>&Delta;<var title="">x</var>=&minus;1</span>
+        and <span>&Delta;<var title="">y</var>=0</span>.</p>
 
-       <dd>
+       </li>
 
-        <p>If the header cell is not anchored in a <a href=#concept-column-group title=concept-column-group>column group</a>, then do
-        nothing.</p>
 
-        <p>Otherwise, let (<var title="">group<sub title="">x</sub></var>, 0) be the slot at which that column
-        group is anchored, let <var title="">width</var> be the number
-        of columns in the column group, and add all the data cells
-        that cover slots with coordinates (<var title="">slot<sub title="">x</sub></var>, <var title="">slot<sub title="">y</sub></var>), where <span><var title="">header<sub title="">x</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">x</sub></var>&nbsp;&lt;&nbsp;<var title="">group<sub title="">x</sub></var>+<var title="">width</var></span> and
-        <span><var title="">header<sub title="">y</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">y</sub></var>&nbsp;&lt;&nbsp;<var title="">y<sub title="">height</sub></var></span>, to the <var title="">data
-        cells</var> list.</p>
+       <!-- VERTICAL -->
 
-       </dd>
+       <li>
 
-       <dt>Otherwise, it is in the <i title="">auto</i> state</dt>
+        <p>For each value of <var title="">x</var> from <var title="">principal<sub title="">x</sub></var> to <span><var title="">principal<sub title="">x</sub></var>+<var title="">principal<sub title="">width</sub></var>-1</span>,
+        run the <a href=#internal-algorithm-for-scanning-and-assigning-header-cells>internal algorithm for scanning and assigning
+        header cells</a>, with the <var title="">principal
+        cell</var>, the <var title="">header list</var>, the initial
+        coordinate (<var title="">x</var>,<var title="">principal<sub title="">y</sub></var>), and the increments <span>&Delta;<var title="">x</var>=0</span> and <span>&Delta;<var title="">y</var>=&minus;1</span>.</p>
 
-       <dd>
+       </li>
 
-        <p>Run these steps:</p>
 
-        <ol><li>
+       <!-- ROW GROUP HEADERS -->
 
-          <p>If the header cell is <a href=#equivalent-to-a-wide-cell>equivalent to a wide
-          cell</a>, let <var title="">header<sub title="">width</sub></var> equal <span><var title="">x<sub title="">width</sub></var>-<var title="">header<sub title="">x</sub></var></span>.</p>
+       <li>
 
-         </li>
+        <p>If the <var title="">principal cell</var> is anchored in a
+        <a href=#concept-row-group title=concept-row-group>row group</a>, then add all
+        header cells that are <a href=#row-group-header title="row group header">row group
+        headers</a> and are anchored in the same row group with an
+        <var title="">x</var>-coordinate less than or equal to
+        <span><var title="">principal<sub title="">x</sub></var>+<var title="">principal<sub title="">width</sub></var>-1</span> and
+        a <var title="">y</var>-coordinate less than or equal to
+        <span><var title="">principal<sub title="">y</sub></var>+<var title="">principal<sub title="">height</sub></var>-1</span> to
+        <var title="">header list</var>.</p>
 
-         <li>
+       </li>
 
-          <p>Let <var title="">x</var> equal <span><var title="">header<sub title="">x</sub></var>+<var title="">header<sub title="">width</sub></var></span>.</p>
 
-         </li>
+       <!-- COLUMN GROUP HEADERS -->
 
-         <li>
+       <li>
 
-          <p>Let <var title="">y</var> equal <span><var title="">header<sub title="">y</sub></var>+<var title="">header<sub title="">height</sub></var></span>.</p>
+        <p>If the <var title="">principal cell</var> is anchored in a
+        <a href=#concept-column-group title=concept-column-group>column group</a>, then
+        add all header cells that are <a href=#column-group-header title="column group
+        header">column group headers</a> and are anchored in the
+        same column group with an <var title="">x</var>-coordinate
+        less than or equal to <span><var title="">principal<sub title="">x</sub></var>+<var title="">principal<sub title="">width</sub></var>-1</span> and a <var title="">y</var>-coordinate less than or equal to <span><var title="">principal<sub title="">y</sub></var>+<var title="">principal<sub title="">height</sub></var>-1</span> to
+        <var title="">header list</var>.</p>
 
-         </li>
+       </li>
 
-         <li>
+      </ol></dd>
 
-          <p><i>Horizontal</i>: If <var title="">x</var> is equal to
-          <var title="">x<sub title="">width</sub></var>, then jump
-          down to the step below labeled <i>vertical</i>.</p>
+    </dl></li>
 
-         </li>
 
-         <li>
+   <!-- CLEANUP -->
 
-          <p>If there is a header cell anchored at (<var title="">x</var>, <var title="">header<sub title="">y</sub></var>) with height <var title="">header<sub title="">height</sub></var>, then jump down to the step
-          below labeled <i>vertical</i>.</p>
+   <li>
 
-         </li>
+    <p>Remove all the <a href=#empty-cell title="empty cell">empty cells</a> from
+    the <var title="">header list</var>.</p>
 
-         <li>
+   </li>
 
-          <p>Add all the data cells that cover slots with coordinates
-          (<var title="">slot<sub title="">x</sub></var>, <var title="">slot<sub title="">y</sub></var>), where <span><var title="">slot<sub title="">x</sub></var>&nbsp;=&nbsp;<var title="">x</var></span> and <span><var title="">header<sub title="">y</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">y</sub></var>&nbsp;&lt;&nbsp;<var title="">header<sub title="">y</sub></var>+<var title="">header<sub title="">height</sub></var></span>, to
-          the <var title="">data cells</var> list.</p>
+   <li>
 
-         </li>
+    <p>Remove any duplicates from the <var title="">header
+    list</var>.</p>
 
-         <li>
+   </li>
 
-          <p>Increase <var title="">x</var> by 1.</p>
+   <li>
 
-         </li>
+    <p>Assign the headers in the <var title="">header list</var> to
+    the <var title="">principal cell</var>.</p>
 
-         <li>
+   </li>
 
-          <p>Jump up to the step above labeled <i>horizontal</i>.</p>
+  </ol><p>The <dfn id=internal-algorithm-for-scanning-and-assigning-header-cells>internal algorithm for scanning and assigning header
+  cells</dfn>, given a <var title="">principal cell</var>, a <var title="">header list</var>, a (<var title="">initial<sub title="">x</sub></var>, <var title="">initial<sub title="">y</sub></var>) initial coordinate, and &Delta;<var title="">x</var> and &Delta;<var title="">y</var> increments, is as
+  follows:<ol><li>
 
-         </li>
+    <p>Let <var title="">x</var> equal <var title="">initial<sub title="">x</sub></var>.</p>
 
-         <li>
+   </li>
 
-          <p><i>Vertical</i>: If <var title="">y</var> is equal to
-          <var title="">y<sub title="">height</sub></var>, then jump
-          to the step below labeled <i>end</i>.</p>
+   <li>
 
-         </li>
+    <p>Let <var title="">y</var> equal <var title="">initial<sub title="">y</sub></var>.</p>
 
-         <li>
+   </li>
 
-          <p>If there is a header cell <var title="">cell</var>
-          anchored at (<var title="">header<sub title="">x</sub></var>, <var title="">y</var>), then follow
-          these substeps:</p>
+   <li>
 
-          <ol><li>
+    <p>Let <var title="">opaque headers</var> be an empty list of
+    cells.</p>
 
-            <p>If the header cell <var title="">cell</var> is
-            <a href=#equivalent-to-a-wide-cell>equivalent to a wide cell</a>, then let <var title="">width</var> be <span><var title="">x<sub title="">width</sub></var>-<var title="">header<sub title="">x</sub></var></span>. Otherwise, let <var title="">width</var> be the width of the header cell <var title="">cell</var>.</p>
+   </li>
 
-           </li>
+   <li>
 
-           <li>
+    <dl class=switch><dt>If <var title="">principal cell</var> is a header cell</dt>
 
-            <p>If <var title="">width</var> is equal to <var title="">header<sub title="">width</sub></var>, then jump
-            to the step below labeled <i>end</i>.</p>
+     <dd><p>Let <var title="">in header block</var> be true, and let
+     <var title="">headers from current header block</var> be a list
+     of cells containing just the <var title="">principal
+     cell</var>.</dd>
 
-           </li>
+     <dt>Otherwise</dt>
 
-          </ol></li>
+     <dd><p>Let <var title="">in header block</var> be false and let
+     <var title="">headers from current header block</var> be an
+     empty list of cells.</p>
 
-         <li>
+    </dl></li>
 
-          <p>Add all the data cells that cover slots with coordinates
-          (<var title="">slot<sub title="">x</sub></var>, <var title="">slot<sub title="">y</sub></var>), where <span><var title="">header<sub title="">x</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">x</sub></var>&nbsp;&lt;&nbsp;<var title="">header<sub title="">x</sub></var>+<var title="">header<sub title="">width</sub></var></span> and
-          <span><var title="">slot<sub title="">y</sub></var>&nbsp;=&nbsp;<var title="">y</var></span>, to the <var title="">data
-          cells</var> list.</p>
+   <li>
 
-         </li>
+    <p><i>Loop</i>: Increment <var title="">x</var> by &Delta;<var title="">x</var>; increment <var title="">y</var> by &Delta;<var title="">y</var>.</p>
 
-         <li>
+    <p class=note>For each invocation of this algorithm, one of
+    &Delta;<var title="">x</var> and &Delta;<var title="">y</var> will
+    be &minus;1, and the other will be 0.</p>
 
-          <p>Increase <var title="">y</var> by 1.</p>
+   </li>
 
-         </li>
+   <li>
 
-         <li>
+    <p>If either <var title="">x</var> or <var title="">y</var> is
+    less than 0, then abort this internal algorithm.</p>
 
-          <p>Jump up to the step above labeled <i>vertical</i>.</p>
+   </li>
 
-         </li>
+   <li>
 
-         <li>
+    <p>If there is no cell covering slot (<var title="">x</var>,
+    <var title="">y</var>), or if there is more than one cell
+    covering slot (<var title="">x</var>, <var title="">y</var>),
+    return to the substep marked <i>loop</i>.</p>
 
-          <p><i>End</i>: Coalesce all the duplicate entries in the
-          <var title="">data cells</var> list, so that each data cell
-          is only present once, in tree order.</p>
+   </li>
 
-         </li>
+   <li>
 
-        </ol></dd>
+    <p>Let <var title="">current cell</var> be the cell covering
+    slot (<var title="">x</var>, <var title="">y</var>).</p>
 
-      </dl></li>
+   </li>
 
-     <li>
+   <li>
 
-      <p>Assign the header cell to all the data cells in the <var title="">data cells</var> list that correspond to
-      <code><a href=#the-td-element>td</a></code> elements that do not have a <code title=attr-td-headers><a href=#attr-td-headers>headers</a></code> attribute specified.</p>
+    <dl class=switch><dt>If <var title="">current cell</var> is a header cell</dt>
 
-     </li>
+     <dd>
 
-    </ol></li>
+      <ol><li><p>Set <var title="">in header block</var> to
+       true.</li>
 
-   <li>
+       <li><p>Add <var title="">current cell</var> to <var title="">headers from current header block</var>.</li>
 
-    <p>For each data cell in the table, in <a href=#tree-order>tree order</a>,
-    run these substeps:</p>
+       <li><p>Let <var title="">blocked</var> be false.</li>
 
-    <ol><li>
+       <li>
 
-      <p>If the data cell corresponds to a <code><a href=#the-td-element>td</a></code> element
-      that does not have a <code title=attr-td-headers><a href=#attr-td-headers>headers</a></code> attribute specified, then
-      skip these substeps and move on to the next data cell (if
-      any).</p>
+        <dl class=switch><dt>If &Delta;<var title="">x</var> is 0</dt>
 
-     </li>
+         <dd>
 
-     <li>
+          <p>If there is no cell in the <var title="">opaque
+          headers</var> list anchored with the same <var title="">x</var>-coordinate as the <var title="">current
+          cell</var>, and with the same width as <var title="">current
+          cell</var>, then let <var title="">blocked</var> be
+          true.</p>
 
-      <p>Otherwise, take the value of the <code title=attr-td-headers><a href=#attr-td-headers>headers</a></code> attribute and <a href=#split-a-string-on-spaces title="split a string on spaces">split it on spaces</a>,
-      letting <var title="">id list</var> be the list of tokens
-      obtained.</p>
+          <p>If the <var title="">current cell</var> is not a
+          <a href=#column-header>column header</a>, then let <var title="">blocked</var> be true.</p>
 
-     </li>
+         </dd>
 
-     <li>
+         <dt>If &Delta;<var title="">y</var> is 0</dt>
 
-      <!-- XXX if nothing was added to this subalgorithm, then make it
-      a single paragraph instead of a nested list. -->
+         <dd>
 
-      <p>For each token in the <var title="">id list</var>, run the
-      following steps:</p>
+          <p>If there is no cell in the <var title="">opaque
+          headers</var> list anchored with the same <var title="">y</var>-coordinate as the <var title="">current
+          cell</var>, and with the same height as <var title="">current cell</var>, then let <var title="">blocked</var> be true.</p>
 
-      <ol><li><p>Let <var title="">id</var> be the token.</li>
+          <p>If the <var title="">current cell</var> is not a
+          <a href=#row-header>row header</a>, then let <var title="">blocked</var> be true.</p>
 
-       <li><p>If there is a header cell in the <a href=#concept-table title=concept-table>table</a> whose corresponding
-       <code><a href=#the-th-element>th</a></code> element has an ID that is equal to the value of
-       <var title="">id</var>, then assign the first such header cell
-       in tree order to the data cell.</li>
+         </dd>
 
-      </ol></li>
+        </dl></li>
 
-    </ol></li>
+       <li><p>If <var title="">blocked</var> is false, then add the
+       <var title="">current cell</var> to the <var title="">headers
+       list</var>.</li>
 
-  </ol><p>A header cell anchored at (<var title="">header<sub title="">x</sub></var>, <var title="">header<sub title="">y</sub></var>) with width <var title="">header<sub title="">width</sub></var> and height <var title="">header<sub title="">height</sub></var> is said to be <dfn id=equivalent-to-a-wide-cell>equivalent to a wide
-  cell</dfn> if all the slots with coordinates (<var title="">slot<sub title="">x</sub></var>, <var title="">slot<sub title="">y</sub></var>), where <span><var title="">header<sub title="">x</sub></var>+<var title="">header<sub title="">width</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">x</sub></var>&nbsp;&lt;&nbsp;<var title="">x<sub title="">width</sub></var></span> and <span><var title="">header<sub title="">y</sub></var>&nbsp;&le;&nbsp;<var title="">slot<sub title="">y</sub></var>&nbsp;&lt;&nbsp;<var title="">header<sub title="">y</sub></var>+<var title="">header<sub title="">height</sub></var></span>, are all either empty or covered
-  by <a href=#empty-data-cell title="empty data cell">empty data cells</a>.<p>A data cell is said to be an <dfn id=empty-data-cell>empty data cell</dfn> if it
-  contains no elements and its text content, if any, consists only of
-  <a href=#white_space>White_Space</a> characters.<p>User agents may remove <a href=#empty-data-cell title="empty data cell">empty data
-  cells</a> when analyzing data in a <a href=#concept-table title=concept-table>table</a>.<h3 id=forms><span class=secno>4.10 </span>Forms</h3><p>Forms allow unscripted client-server interaction: given a form, a
+      </ol></dd>
+
+     <dt>If <var title="">current cell</var> is a data cell and <var title="">in header block</var> is true</dt>
+
+     <dd><p>Set <var title="">in header block</var> to false. Add
+     all the cells in <var title="">headers from current header
+     block</var> to the <var title="">opaque headers</var> list, and
+     empty the <var title="">headers from current header block</var>
+     list.</p>
+
+    </dl></li>
+
+   <li>
+
+    <p>Return to the step marked <i>loop</i>.</p>
+
+   </li>
+
+  </ol><p>A header cell anchored at the slot with coordinate (<var title="">x</var>, <var title="">y</var>) with width <var title="">width</var> and height <var title="">height</var> is said
+  to be a <dfn id=column-header>column header</dfn> if any of the following conditions
+  are true:<ul><li>The cell's <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attribute
+   is in the <a href=#attr-th-scope-col title=attr-th-scope-col>column</a> state</li>
+
+   <li>The cell's <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attribute
+   is in the <a href=#attr-th-scope-auto title=attr-th-scope-auto>auto</a> state, and
+   there are no data cells in any of the cells covering slots with
+   <var title="">y</var>-coordinates <var title="">y</var>
+   .. <span><var title="">y</var>+<var title="">height</var>-1</span>.</li>
+
+  </ul><p>A header cell anchored at the slot with coordinate (<var title="">x</var>, <var title="">y</var>) with width <var title="">width</var> and height <var title="">height</var> is said
+  to be a <dfn id=row-header>row header</dfn> if any of the following conditions
+  are true:<ul><li>The cell's <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attribute
+   is in the <a href=#attr-th-scope-row title=attr-th-scope-row>row</a> state</li>
+
+   <li>The cell's <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attribute
+   is in the <a href=#attr-th-scope-auto title=attr-th-scope-auto>auto</a> state, and
+   the cells is not a <a href=#column-header>column header</a>, and there are no
+   data cells in any of the cells covering slots with <var title="">x</var>-coordinates <var title="">x</var> .. <span><var title="">x</var>+<var title="">width</var>-1</span>.</li>
+
+  </ul><p>A header cell is said to be a <dfn id=column-group-header>column group header</dfn> if
+  its <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attribute is in the
+  <a href=#attr-th-scope-colgroup title=attr-th-scope-colgroup>column group</a> state.<p>A header cell is said to be a <dfn id=row-group-header>row group header</dfn> if
+  its <code title=attr-th-scope><a href=#attr-th-scope>scope</a></code> attribute is in the
+  <a href=#attr-th-scope-rowgroup title=attr-th-scope-rowgroup>row group</a> state.<p>A cell is said to be an <dfn id=empty-cell>empty cell</dfn> if it contains no
+  elements and its text content, if any, consists only of
+  <a href=#white_space>White_Space</a> characters.<h3 id=forms><span class=secno>4.10 </span>Forms</h3><p>Forms allow unscripted client-server interaction: given a form, a
   user can provide data, submit it to the server, and have the server
   act on it accordingly (e.g. returning the results of a search or
   calculation). The elements used in forms can also be used for user
Received on Saturday, 20 December 2008 09:25:18 GMT

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