XML

⸺ by Charles Iliya Krempeaux

XML, short for Extensible Markup Language, refers to a couple of different things.

The first is that XML is a and much like . What used to be one of the more popular examples of this is — . But many, many others exist, too, including — , , , , , , , , , , , , , , and many others.

The second is that XML is a paradigm for creating s.

Early XML Misconceptions

At the time when XML was being created, it was believed by many (including myself) that XML would be a way for web developers to create new tags and elements for HTML. This turned out to be a somewhat naive view of XML. Coming from that point-of-view, it seems that XML turned out to sometimes be a way of creating alternates to HTML. (Although XML's applicaions go beyond this..)

Common XML Use-Cases

Today XML has found much popularity as a way of developing interchange formats; as a platform and paradigm neutral way of communicating; and as a language for creating languages.

XML versus Semantic HTML

Some have argued that XML is unneeded. That all one needs to do is use (which could include ). And although I believe that the use of is powerful; I believe that it is not always a good replaced for XML. The reason for this is that parsing is much much more complex than parsing XML. Which means that, although a beginner could create a (wrong but working) XML parser — a begineer would have great difficulty creating a parser. The learning curve to create a parser is much much steeper than the leaning curve for parsing XML.

Because of this I believe that in many situations XML is a better choice than Semantic HTML because XML allows for quick adoption of many kinds of technologies based on it (because of the ease with which parsers can be written). Having said that, however, there still are many many situations where Semantic HTML it the better choice. (These are situations where developers do NOT have to write parsers to parse the Semantic HTML. Many of these could be characterized by calling them in-browser technologies. Technologies that rely on the browsers CSS or JavaScript facilities for parsing the Semantic HTML.)

Decline Of XML

Rather than being used for s, such as something like this —

	<?xml version="1.0"?>
	
	<message>
		I am writing <italics>this</italics> message to <name><given-name>Joe</given-name> <family-name>Blow</family-name></name>.
	</message>

— XML was very very commonly used to encode ; such as something like this —

	<?xml version="1.0"?>
	
	<address>
		<locality>North Pole</locality>
		<region>Nunavut</region>
		<country-name>Canada</country-name>
		<postal-code>H0H 0H0</postal-code>
	</address>

This drew criticism. The jist of those criticisms was that — XML was too verbose, and made file sizes much much larger than necessary.

largely replaced XML for the use-case of encoding . Including when based APIs returned data — rather than returning they retutned .

But also has its own problems and issues.