What is XML?

XML stands for Extensible Markup Language, which can be a bit misleading in that XML isn't so much a language as it is a meta-language.  Specifically, though XML is a method of communication, it does not actually define any meanings.  Rather, the meaning of the contents of an XML document must already be understood between the sender and recipient in order for there to be any informed action.  For example, if I write that I have a bag with two apples, a banana and a peach, you are able to rationally determine that it would be helpful for me to have a knife and a peeler in order to make fruit salad.  You can determine this because my writing and your reading what I've written in English allows you to grasp the meaning of my having a bag of fruit.  If I was to write that I have a ____ with ______, _______ and _______, you would not know the meaning of the sentence unless you already knew with what the blanks would be filled.  XML, in essence, provides a framework for defining such sets of blanks.  To extend the example, in XML I could write that I have:

<container name="bag">
   	<item count="2">apple</item>
   	<item count="1">banana</item>
   	<item count="1">peach</item>
</container> 

Assuming that the reader of the text knows what a container, bag, item, count, 1, 2, apple, banana and peach are, the reader could then use the framework provided by XML to determine the meaning of the text.

• What is XHTML?

• Languages Markup XML