Disambiguate attribute declarations from content attributes

The change updates the spec to use the term “attribute declaration” in
all cases where what the spec is referring to is actually the syntax for
declaring attributes in markup.

Otherwise, without this change, the spec uses the same term “attribute”
to refer both to attribute declarations in markup and to actual content
attributes as they exist in the DOM.

And we have evidence of authors being confused due to that ambiguous use
of the same term to refer to different things — and evidence suggesting
the ambiguous usage promotes the wrong mental model of HTML for authors.

source

@@ -677,11 +677,11 @@ interface <dfn data-x="">Example</dfn> {
 
   <pre><code class="html">&lt;a href="demo.html">simple&lt;/a></code></pre>
 
-  <p><span data-x="syntax-attributes">Attributes</span> are placed inside the start tag, and consist
-  of a <span data-x="syntax-attribute-name">name</span> and a <span
-  data-x="syntax-attribute-value">value</span>, separated by an "<code data-x="">=</code>" character.
-  The attribute value can remain <a href="#unquoted">unquoted</a> if it doesn't contain <span>ASCII
-  whitespace</span> or any of <code data-x="">"</code> <code data-x="">'</code> <code
+  <p><span data-x="syntax-attribute-declarations">Attribute declarations</span> are placed inside
+  the start tag, and consist of a <span data-x="syntax-attribute-name">name</span> and a <span
+  data-x="syntax-attribute-value">value</span>, separated by an "<code data-x="">=</code>"
+  character.  The attribute value can remain <a href="#unquoted">unquoted</a> if it doesn't contain
+  <span>ASCII whitespace</span> or any of <code data-x="">"</code> <code data-x="">'</code> <code
   data-x="">`</code> <code data-x="">=</code> <code data-x="">&lt;</code> or <code
   data-x="">&gt;</code>. Otherwise, it has to be quoted using either single or double quotes. The
   value, along with the "<code data-x="">=</code>" character, can be omitted altogether if the value
@@ -1174,8 +1174,8 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
     <div class="example">
 
      <p>For example, this is why the U+0060 GRAVE ACCENT character (`) is not allowed in unquoted
-     attributes. In certain legacy user agents, <!-- namely IE --> it is sometimes treated as a
-     quote character.</p>
+     attribute declarations. In certain legacy user agents, <!-- namely IE --> it is sometimes
+     treated as a quote character.</p>
 
     </div>
 
@@ -1246,18 +1246,18 @@ a.setAttribute('href', 'https://example.com/'); // change the content attribute
 
     <div class="example">
 
-     <p>For example, "attributes" in end tags are ignored currently, but they are invalid, in case a
-     future change to the language makes use of that syntax feature without conflicting with
-     already-deployed (and valid!) content.</p>
+     <p>For example, attribute declarations in end tags are ignored currently, but they are invalid,
+     in case a future change to the language makes use of that syntax feature without conflicting
+     with already-deployed (and valid!) content.</p>
 
     </div>
    </dd>
   </dl>
 
-  <p>Some authors find it helpful to be in the practice of always quoting all attributes and always
-  including all optional tags, preferring the consistency derived from such custom over the minor
-  benefits of terseness afforded by making use of the flexibility of the HTML syntax. To aid such
-  authors, conformance checkers can provide modes of operation wherein such conventions are
+  <p>Some authors find it helpful to be in the practice of always quoting all attribute values and
+  always including all optional tags, preferring the consistency derived from such custom over the
+  minor benefits of terseness afforded by making use of the flexibility of the HTML syntax. To aid
+  such authors, conformance checkers can provide modes of operation wherein such conventions are
   enforced.</p>
 
 
@@ -45441,7 +45441,8 @@ interface <dfn interface>HTMLTableCellElement</dfn> : <span>HTMLElement</span> {
 
   <p class="note">There is no particular significance to the way some of the attributes have their
   values quoted and others don't. The HTML syntax allows a variety of equally valid ways to specify
-  attributes, as discussed <span data-x="syntax-attributes">in the syntax section</span>.</p>
+  attributes, as discussed <span data-x="syntax-attribute-declarations">in the syntax
+  section</span>.</p>
 
   <p>For example, if the customer entered "Denise Lawrence" as their name, "555-321-8642" as their
   telephone number, did not specify an email address, asked for a medium-sized pizza, selected the
@@ -122895,17 +122896,17 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
    <li>The next few characters of a start tag must be the element's <span
    data-x="syntax-tag-name">tag name</span>.</li>
 
-   <li>If there are to be any attributes in the next step, there must first be one or more
-   <span>ASCII whitespace</span>.</li>
+   <li>If there are to be any attribute declarations in the next step, there must first be one or
+   more <span>ASCII whitespace</span>.</li>
 
-   <li>Then, the start tag may have a number of attributes, the <span
-   data-x="syntax-attributes">syntax for which</span> is described below. Attributes must be
-   separated from each other by one or more <span>ASCII whitespace</span>.</li>
+   <li>Then, the start tag may have a number of attribute declarations, the <span
+   data-x="syntax-attribute-declarations">syntax for which</span> is described below. Attribute
+   declarations must be separated from each other by one or more <span>ASCII whitespace</span>.</li>
 
-   <li>After the attributes, or after the <span data-x="syntax-tag-name">tag name</span> if there
-   are no attributes, there may be one or more <span>ASCII whitespace</span>. (Some attributes are
-   required to be followed by a space. See the <span data-x="syntax-attributes">attributes
-   section</span> below.)</li>
+   <li>After the attribute declarations, or after the <span data-x="syntax-tag-name">tag name</span>
+   if there are no attributes, there may be one or more <span>ASCII whitespace</span>. (Some
+   attribute declarations are required to be followed by a space. See the <span
+   data-x="syntax-attribute-declarations">attribute declarations</span> section below.)</li>
 
    <li>Then, if the element is one of the <span>void elements</span>, or if the element is a <span
    data-x="foreign elements">foreign element</span>, then there may be a single U+002F SOLIDUS
@@ -122938,10 +122939,10 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
   </ol>
 
 
-  <h5>Attributes</h5>
+  <h5>Attribute declarations</h5>
 
-  <p><dfn data-x="syntax-attributes">Attributes</dfn> for an element are expressed inside the
-  element's start tag.</p>
+  <p><dfn data-x="syntax-attribute-declarations">Attribute declarations</dfn> for an element are
+  expressed inside the element's start tag.</p>
 
   <p>Attributes have a name and a value. <dfn data-x="syntax-attribute-name">Attribute names</dfn>
   must consist of one or more characters other than <span data-x="control">controls</span>,
@@ -122955,7 +122956,7 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
   except with the additional restriction that the text cannot contain an <span
   data-x="syntax-ambiguous-ampersand">ambiguous ampersand</span>.</p>
 
-  <p>Attributes can be specified in four different ways:</p>
+  <p>Attributes can be declared in four different ways:</p>
 
   <dl>
    <dt>Empty attribute syntax</dt>
@@ -122973,8 +122974,8 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
 
     </div>
 
-    <p>If an attribute using the empty attribute syntax is to be followed by another attribute, then
-    there must be <span>ASCII whitespace</span> separating the two.</p>
+    <p>If an attribute declaration using the empty attribute syntax is to be followed by another
+    attribute declaration, then there must be <span>ASCII whitespace</span> separating the two.</p>
    </dd>
 
    <dt id="unquoted">Unquoted attribute value syntax</dt>
@@ -123026,9 +123027,9 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
 
     </div>
 
-    <p>If an attribute using the unquoted attribute syntax is to be followed by another attribute or
-    by the optional U+002F SOLIDUS character (/) allowed in step 6 of the <span
-    data-x="syntax-start-tag">start tag</span> syntax above, then there must be <span>ASCII
+    <p>If an attribute declaration using the unquoted attribute syntax is to be followed by another
+    attribute declaration or by the optional U+002F SOLIDUS character (/) allowed in step 6 of the
+    <span data-x="syntax-start-tag">start tag</span> syntax above, then there must be <span>ASCII
     whitespace</span> separating the two.</p>
    </dd>
 
@@ -123052,8 +123053,9 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
 
     </div>
 
-    <p>If an attribute using the single-quoted attribute syntax is to be followed by another
-    attribute, then there must be <span>ASCII whitespace</span> separating the two.</p>
+    <p>If an attribute declaration using the single-quoted attribute syntax is to be followed by
+    another attribute declaration, then there must be <span>ASCII whitespace</span> separating the
+    two.</p>
    </dd>
 
    <dt>Double-quoted attribute value syntax</dt>
@@ -123076,13 +123078,14 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
 
     </div>
 
-    <p>If an attribute using the double-quoted attribute syntax is to be followed by another
-    attribute, then there must be <span>ASCII whitespace</span> separating the two.</p>
+    <p>If an attribute declaration using the double-quoted attribute syntax is to be followed by
+    another attribute declaration, then there must be <span>ASCII whitespace</span> separating the
+    two.</p>
    </dd>
   </dl>
 
-  <p>There must never be two or more attributes on the same start tag whose names are an <span>ASCII
-  case-insensitive</span> match for each other.</p>
+  <p>There must never be two or more attribute declarations in the same start tag whose names are an
+  <span>ASCII case-insensitive</span> match for each other.</p>
 
   <hr>
 
@@ -123858,14 +123861,15 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
     <tr>
      <td><dfn data-x="parse-error-duplicate-attribute">duplicate-attribute</dfn>
      <td><p>This error occurs if the parser encounters an <span
-     data-x="syntax-attributes">attribute</span> in a tag that already has an attribute with the
-     same name. The parser ignores all such duplicate occurrences of the attribute.
+     data-x="syntax-attribute-declarations">attribute declaration</span> in a tag that already has
+     an attribute with the same name. The parser ignores all such duplicate occurrences of the
+     attribute.
 
     <tr>
      <td><dfn data-x="parse-error-end-tag-with-attributes">end-tag-with-attributes</dfn>
      <td><p>This error occurs if the parser encounters an <span data-x="syntax-end-tag">end
-     tag</span> with <span data-x="syntax-attributes">attributes</span>. Attributes in end tags are
-     ignored and do not make their way into the DOM.</p>
+     tag</span> with <span data-x="syntax-attribute-declarations">attribute declarations</span>.
+     Attribute declarations in end tags are ignored and do not result in attributes in the DOM.</p>
 
     <tr>
      <td><dfn data-x="parse-error-end-tag-with-trailing-solidus">end-tag-with-trailing-solidus</dfn>
@@ -123977,7 +123981,7 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
     <tr>
      <td><dfn data-x="parse-error-missing-attribute-value">missing-attribute-value</dfn>
      <td><p>This error occurs if the parser encounters a U+003E (>) <span>code point</span> where an
-     <span data-x="syntax-attributes">attribute</span> value is expected (e.g., <code
+     <span data-x="syntax-attribute-value">attribute value</span> is expected (e.g., <code
      data-x="">&lt;div id=></code>). The parser treats the attribute as having an empty value.</p>
 
     <tr>
@@ -124064,7 +124068,7 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
     <tr>
      <td><dfn data-x="parse-error-missing-whitespace-between-attributes">missing-whitespace-between-attributes</dfn>
      <td><p>This error occurs if the parser encounters <span
-     data-x="syntax-attributes">attributes</span> that are not separated by <span>ASCII
+     data-x="syntax-attribute-declarations">attributes</span> that are not separated by <span>ASCII
      whitespace</span> (e.g., <code data-x="">&lt;div id="foo"class="bar"></code>). In this case the
      parser behaves as if ASCII whitespace is present.</p>
 
@@ -124251,7 +124255,7 @@ dictionary <dfn dictionary>StorageEventInit</dfn> : <span>EventInit</span> {
     <tr>
      <td><dfn data-x="parse-error-unexpected-solidus-in-tag">unexpected-solidus-in-tag</dfn>
      <td><p>This error occurs if the parser encounters a U+002F (/) <span>code point</span> that is
-     not a part of a quoted <span data-x="syntax-attributes">attribute</span> value and not
+     not a part of a quoted <span data-x="syntax-attribute-value">attribute value</span> and not
      immediately followed by a U+003E (>) code point in a tag (e.g., <code data-x="">&lt;div /
      id="foo"></code>). In this case the parser behaves as if it encountered <span>ASCII
      whitespace</span>.</p>