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> Picking up Mike Champion's question about how to communicate that XML is, so
> it is suggested, "simple" let's have a challenge for list members to explain
> XML in 500 words to someone who is a Web developer but has no formal CS
XML is a common alphabet and grammar ("syntax") for newer Web
development standards like SVG (a common vector graphics format for the
Web), XForms (the next generation of Web forms) and RSS (a way to
summarize the information on your site so that "subscribers" can find
out about documents added to the site).
Before XML was popular, it was common to invent new syntaxes from
scratch. Learning, implementing and using new syntaxes can be quite
challenging so this process was very inefficient.
For instance before SVG, it was common to do vector graphics in
PostScript. If you compare these SVG and Postscript examples you'll see
that the SVG example has much more in common with the HTML you already
know than the Postscript:
Tools for working with HTML (especially its XHTML variant) can more
easily be adapted for working with SVG than with something totally
different like Postscript.
XML goes well beyond web interface development standards. It is also
used under the covers for many machine to machine communications such as
automated purchasing. The benefits there are similar.
Compare a purchase order in the older EDI syntax:
to the markup-based one in XML:
Similarly, compare the line-based syntax MCF to RSS:
Each of these standards (SVG for graphics, RSS for syndication, ebXML
for electronic business) can be considered a "vocabulary". Just as it is
more efficient to invent new words for English than to invent a whole
new language, it is more efficient to invent new vocabularies for XML
than invent whole new syntaxes.
Vocabularies in English are defined in glossaries or dictionaries.
Similarly, vocabularies in XML are defined in so-called "schemas". Just
as there are a variety of formats for glossaries, there are a variety of
"schema languages" for defining XML vocabularies. The existence of
schema languages serves to encourage an important best-practice:
documentation of vocabularies! Before XML, it was common for the syntax
and vocabulary of data formats to be completely proprietary trade
secrets (consider the Office document file format). This is no longer
considered an acceptable practice and Microsoft Office 11 is expected to
have a fully-documented XML file-format (and perhaps a formal schema).
XML also encourages best practices around internationalization. XML
builds on a standard for characters known as "Unicode." Using XML (and
thus Unicode), it is easy to insert characters in anything from Arabic
to Chinese to Cyrllic and even from ancient dead languages! This is an
important step forward in an industry that has historically thought of
English first and then other languages only much later.