Make unknown elements render exactly as if they were a g element. Closes

 #122.

master/definitions.xml

@@ -526,7 +526,7 @@
 
   <!-- ... element categories ............................................ -->
 
-  <elementcategory name='container' href='struct.html#TermContainerElement' elements='svg, g, defs, symbol, clipPath, mask, pattern, marker, a, switch'/>
+  <elementcategory name='container' href='struct.html#TermContainerElement' elements='svg, g, defs, symbol, clipPath, mask, pattern, marker, a, switch, unknown'/>
   <elementcategory name='descriptive' href='struct.html#TermDescriptiveElement' elements='desc, title, metadata'/>
   <elementcategory name='gradient' href='pservers.html#TermGradientElement' elements='linearGradient, radialGradient, mesh'/>
   <elementcategory name='graphics' href='struct.html#TermGraphicsElement' elements='path, text, rect, circle, ellipse, line, polyline, polygon, image, use, foreignObject, iframe, video, audio, canvas'/>

master/struct.html

@@ -349,10 +349,19 @@ <h2 id="UnknownElement">Unknown elements</h2>
 
 <edit:elementsummary name='unknown'/>
 
-<p>The <a>SVGUnknownElement</a> interface must be used for elements in the SVG namespace that are not defined by this specification.</p>
-<p>Known elements in the SVG namespace that occur in places where SVG's content model doesn't explicitly allow it must not render.</p>
-<p>Unknown elements in the SVG namespace render as if the unknown element was a <a>'g'</a> element.</p>
-<p>Known and unknown elements in other namespaces that occur as a child of any SVG element except <a>'foreignObject'</a>, must not render unless
+<p>Unknown elements are all elements that are in the SVG namespace that are not
+defined by this specification or any SVG module. The <a>SVGUnknownElement</a>
+interface must be used for unknown elements.</p>
+<p>Known elements in the SVG namespace that occur in places where SVG's content
+model doesn't explicitly allow it must not render.</p>
+<p>Unknown elements in the SVG namespace must render as if the unknown element
+were replaced with a <a>'g'</a> element. This means that any attribute or
+property that is valid on the <a>'g'</a> element is also valid on unknown
+elements, and any styles specified on unknown elements must be inherited by
+their child elements.  Unknown elements are <a>container elements</a>.
+</p>
+<p>Known and unknown elements in other namespaces that occur as a child of any
+SVG element except <a>'foreignObject'</a>, must not render unless
 explicitly stated otherwise in this specification.</p>
 
 <p>Consequently, in the following example:</p>
@@ -369,9 +378,6 @@ <h2 id="UnknownElement">Unknown elements</h2>
 
 <edit:example href='images/struct/unknownelms01.svg' image='no' link='yes'/>
 
-<p class="issue" data-issue="64">Do we need to mention anything about attributes, properties and such on SVGUnknownElements?</p>
-<p class="issue" data-issue="65">Should SVGUnknownElement be a <a>container element</a>?</p>
-
 <h2 id="Head">Defining content for reuse, and the <span class='element-name'>'defs'</span> element</h2>
 
 <h3 id="Overview">Overview</h3>