Re: [9fans] xml

[Russ Cox <rsc@swtch.com>]

On Mon, Jun 28, 2010 at 9:19 AM, hugo rivera <uair00@gmail.com> wrote:
> If you haven't heard of XML yet, you must be living under a rock!  -
> Programming in the .NET Environment
> Taken from the fortunes file. I guess I must be living under a rock,
> but I don't know what xml is, or pragmatically, what is it for.

XML is what it looks like: it's a textual markup language like HTML.
It's ill-suited for representing data structures (an XML element is an
order-dependent collection of anonymous values, while a data structure
is an order-independent collection of named values), but that hasn't
stopped a very large number of applications from using it as a data
structure serialization format.  (Just to take one example out of many,
Apple's Keynote presentation files are named .key but are actually .zip
files containing a (compressed) XML file and supporting media.)

Unlike HTML, there is not a fixed set of allowed tag names or attributes.
Each program that generates or parses XML is free to pick whatever
names it likes; raw XML doesn't even begin to make sense unless
you know the meanings assigned to the tags.  (This problem is
fundamental to any data description, not a flaw in XML, but I mention
it so you won't think you need to find the official definition of the
semantics of XML.)

Russ