I just finished writing last month's Extreme XML column*
entitled The XML Litmus Test: Understanding When and Why to Use
XML. The article is a more formal write up from my weblog post
The XML Litmus Test expanded to contain examples of appropriate
and inappropriate uses of XML as well as with some of the
criteria for choosing XML fleshed out. Below is an excerpt from
the article which contains the core bits that I hope everyone
who reads it remembers    XML is the appropriate tool for the
job if the following criteria are satisfied by choosing XML as
the data representation format for a given application.  1.     
there is a need to interoperate across multiple software
platforms  2.      one or more of the off-the-shelf tools for
dealing with XML can be leveraged when producing or consuming
the data  3.      parsing performance is not critical  4.     
the content is not primarily binary content such as a music or
image file  5.      the content does not contain control
characters or any other characters tha