XML: The Mother of All Web Languages




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Ceponkus, Hoodbhoy - Applied XML - Toolkit for Programmers

XML: The Mother of All Web Languages
In the most basic sense, XML is not so much a computer language as a standard for 
defining all other markup languages. 
Markup languages
is a generic term that is roughly 
applied to all information transmission languages that are text-based and use special text 
characters (markup) that contain additional information about the content from the raw 
content (data) itself.
To put things in perspective, let’s use a concept with which we’re pretty familiar: human 
languages. Just as the human speech apparatus can create an infinite number of 
sounds, only a finite set of those sounds when used in a finite set of arrangements can 
be understood in terms of human speech. You can make many noises with your mouth 
but in order to communicate, you need to speak words and sentences, all of which are 
members of the set called language. There are many languages. Languages are defined 
by society and each society is different. For each language, a finite (though expandable) 
list of words is created in the shape of dictionaries. In addition, the language dictates 
something called grammar, which classifies and controls the way these words can be 
arranged. One part of grammar is punctuation, which gives us additional information to 
help us differentiate sentences and words.
Coming back to the computer world, we’ve come to accept that alphanumeric text is the 
easiest format to transmit data so that computing devices can interpret it (using Unicode, 
we’re not limited to English characters—more on that later in this chapter). In terms of our 
analogy, think of these alphanumeric characters as sounds that the human speech 
apparatus can create. Think of markup as punctuation.

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XML comes in at a level above society (something that humans would never accept). 
XML dictates exactly how languages can be created; that is, it defines a grammar that all 
other languages must follow. The key point here is that the grammar the XML defines is 
flexible enough for each language to create its own dictionary and grammar.
This is incredibly important. Using our analogy again, XML has essentially achieved the 
equivalent of describing a way for creating virtually all human languages such that each 
can functionally remain as it is now and simultaneously provide a way for everyone to 
understand one another. Essentially, all languages become dialects of one base 
language. Figure 2.3 illustrates this idea.

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