clarify img mappings

index.html

@@ -2964,12 +2964,23 @@ <h4 id=el-img>`img`</h4>
     <tr>
       <th>[[wai-aria-1.2]]</th>
       <td>
-        <a class="core-mapping" href="#role-map-image">`image`</a>
-        or  <a class="core-mapping" href="#role-map-img">`img`</a>role
+        <div>
+          If element has a non-empty `src` or `srcset` attribute, an <a data-cite="accname-1.2/#dfn-accessible-name">accessible name</a>, or both, 
+          then map to the <a class="core-mapping" href="#role-map-image">`image`</a>
+          or <a class="core-mapping" href="#role-map-img">`img`</a> role.
+        </div>
+        <div>
+          Otherwise, if the element has no `src` or `srcset` attribute, or if the attribute(s) are set to the empty string, and the `img` has 
+          no `alt` attribute or accessible name, then map to the <a class="core-mapping" href="#role-map-none">`none`</a>  
+          or <a class="core-mapping" href="#role-map-presentation">`presentation`</a> role.
+        </div>
       </td>
     </tr>
     <tr>
-      <th><a href="https://msdn.microsoft.com/en-us/library/dd373608%28v=VS.85%29.aspx">MSAA</a> + <a href="http://accessibility.linuxfoundation.org/a11yspecs/ia2/docs/html/">IAccessible2</a></th>
+      <th>
+        <a href="https://msdn.microsoft.com/en-us/library/dd373608%28v=VS.85%29.aspx">MSAA</a> + 
+        <a href="http://accessibility.linuxfoundation.org/a11yspecs/ia2/docs/html/">IAccessible2</a>
+      </th>
       <td>
         <div class="general">Use WAI-ARIA mapping</div>
       </td>
@@ -2996,6 +3007,8 @@ <h4 id=el-img>`img`</h4>
     <tr>
       <th>Comments</th>
       <td>
+        <p>An `img` with a valid `src`, `srcset`, or both and no `alt` attribute or <a data-cite="accname-1.2/#dfn-accessible-name">accessible name</a> will still map to 
+        the `image` role, unless another role has been explicitly provided by an author.</p>
         <p class="note">
           ARIA 1.3 adds the `image` role as the preferred synonym to the ARIA 1.0 `img` role.
           The expected computed role for named `img` elements is now "image".
@@ -3004,15 +3017,17 @@ <h4 id=el-img>`img`</h4>
     </tr>
   </tbody>
 </table>
-<h4 id=el-img-empty-alt>`img` <span class="el-context">(`alt`attribute value is an empty string, i.e. `alt=""` or `alt` with no value in the markup)</span></h4>
+<h4 id=el-img-empty-alt>`img` <span class="el-context">(<a data-cite="html/embedded-content.html#attr-img-alt">`alt`</a>
+                attribute value is an empty string)</span>
+</h4>
 <table aria-labelledby=el-img-empty-alt>
   <tbody>
     <tr>
       <th>HTML Specification</th>
       <td>
         <a data-cite="html">`img`</a>
         <span class="el-context">(<a data-cite="html/embedded-content.html#attr-img-alt">`alt`</a>
-                attribute value is an empty string, i.e. `alt=""` or `alt` with no value in the markup)</span>
+        attribute value is an empty string.)</span>
       </td>
     </tr>
     <tr>
@@ -3051,7 +3066,10 @@ <h4 id=el-img-empty-alt>`img` <span class="el-context">(`alt`attribute value is
     <!-- <th><a href="#accessible-name-and-description-computation">Naming Algorithm</a></th> -->
     <tr>
       <th>Comments</th>
-      <td>
+      <td class="comments">
+        <p>Authors can specify the `alt` attribute to be the empty string by either marking it up as `alt=""` or `alt` with no value.</p>
+        <p>If an `img` has been provided an `alt=""`, but also has an `aria-label` or `aria-labelledby` attribute specified which returns an 
+        accessible name, then the element maps to the `img` role.</p>
       </td>
     </tr>
   </tbody>