Shedding some light on XML

Calling XML a single web technology does it quite a disservice. XHMTL (what you are reading now) is a variant of XML. Other important XML variants for the web are "RSS, MathML, GraphML, Scalable Vector Graphics (SVG), MusicXML" and there are "thousands of others" (Wikipedia, XML). The W3C maintains documents on MathML, InkML and SVG.

The bottom line on usability:

Know which version of XML you are using. If you are using a standard, make sure you know which browsers work with the standard. If you are creating your own, use with caution.

More on Usability:

One type of XML that many people have seen on the net is RSS, even if they haven't subscribed to a feed themselves. If you are a web developer and you set up an RSS feed for your site, this is how user could set things up Firefox:

RSS is pretty usable from the browser side, but what about trying to few another XML file on the web?

A look at the difference in XML parsing in Firefox and Safari:

You can find this page at http://seashore.sourceforge.net/swlml.xml. Notice that on the right Firefox shows the links correctly. On the left, however, Safari chokes and shows neither links nor the bullets correctly (or maybe those are the right bullets...). Both browsers view the items in brackets as objects similar to pictures, which seems odd to me. This particular example of "poor" XML design is particularly egregious because Seashore is designed for Mac and Safari is the default Mac browser. Since the XML validates via the XML validator at http://www.w3schools.com/xml/xml_validator.asp (if you want to test yourself, make sure you change relative links to absolute links), it's really Safari's fault, but the web designers should know that many of their patrons will be using Safari. Under the hood, the XML looks a lot like XHTML.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE software SYSTEM "swlml-0.9.dtd" [
  <!ENTITY at "@"> ]>
<?xml-stylesheet type="text/css" href="swlml-css-0.9.css"?>

<software xmlns:xlink="http://www.w3.org/1999/xlink">
	<name>Seashore</name>
	<version>0.1.8</version>
	<category>
	
	<item>Multimedia::Graphics::Editors::Raster-Based</item>

	</category>

... more code ...

	<languages>
		<language>
			<name>English</name>
			<iso639>en</iso639>
		</language>
		<language>
			<name>Slovak</name>

			<iso639>sk</iso639>
		</language>
	</languages>
</software>

	
	

Just for fun, I decided to look at it in Internet Exploder.



Notice that the headings "Name", "Category," "License," "Distributor" are nowhere to be found. Wonder why the browser got its nickname? Remember, this is valid XML.

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