A user agent (UA) might not have the ability to process and view SVG documents. The following list outlines two of the backwards compatibility scenarios associated with SVG documents:
This <switch> element and feature-availability test facility (or their equivalents) are the recommended way for XML authors to provide an alternate representation to an SVG document, such as an image or a text string. The following example shows how to embed an SVG drawing within a SMIL 1.0 document such that an alternate image will display in the event the UA doesn't support SVG. (In this example, the SVG document is included via a URL reference. With some parent XML grammars it will also be possible to include an SVG document inline within the same file as its parent grammar.)
<?xml version="1.0" standalone="yes"?>
<smil>
<body>
<!-- The SMIL <switch> element will process the
first child element which tests true and skip
past all others. -->
<switch>
<!-- The system-required attribute tests to see if
the user agent supports SVG. If true, then
render the file drawing.svg. -->
<ref system-required="http://www.w3.org/Graphics/SVG/SVG-19990812.dtd"
type="image/svg" src="drawing.svg" />
<!-- Else, render the alternate image. -->
<img src="alternate_image.jpg" />
</switch>
</body>
</smil>
For HTML 4.0, SVG drawings should be embedded using the <object> element. The alternate representation should be included as the content of the <object> element. In this case, the SVG document usually will be included via a URL reference. The following example shows how to use the <object> element to include an SVG drawing via a URL reference with an image serving as the alternate representation in the absence of an SVG user agent:
<html>
<body>
<object type="image/svg" data="drawing.svg">
<!-- The contents of the <object> element (i.e., an alternate
image) are drawn in the event the user agent cannot process
the SVG drawing. -->
<img src="alternate_image.jpg" alt="short description" />
</object>
</body>
</html>