Not using mixed content? Then don't use XML

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

First a few definitions:

----------------
Sweet spot 
----------------
    A place where there a maximum response for 
    a given amount of effort.

--------------------
Mixed content
--------------------
    An element has mixed content if its content is a 
    mix of data and elements. Here is an example of 
    mixed content:

    <condition>The patient exhibited <emp>extreme</emp> 
                       arrhythmia</condition>

--------------------------------------------------------------
Data-centric versus Document-centric content
--------------------------------------------------------------
    Data-centric content is where there is no mixed content, 
    document-centric content is where there is mixed content.

-----------------------------
Semi-structured data 
-----------------------------
    A synonym for mixed content.


Okay, now for the issue at hand:

    Should you use XML?


Sean McGrath says [1]:

    XML's sweet spot is mixed content. 

    If you are not using mixed content, then there 
    are a trillion and one ways of representing data-centric 
    content, most programming languages do it out-of-the-box.

    If you absolutely, totally, never, ever will need mixed 
    content then there are sane alternatives to XML. 

    There always has been alternatives, from humble CSV up to 
    fancier JSON/Python/Ruby direct data expression languages.

    A huge chunk of the world doesn't need mixed content or 
    even know what it is. 

    It has always been a source of worry that folks with perfectly 
    good relational data sets have felt compelled by buzz-pressure 
    to put their content into XML - very little gain in the general case.


Professor Daniel Lemire says [2]:

    XML is great for dealing with semi-structured data.

    Alas, we ended up torturing XML by applying it to ill-suited 
    purposes. 

    We must learn how to select the best format. Does your data 
    look like a table? Can a flat file do the job? Do you need a 
    key-value format like JSON? Or maybe a simple text file? 
    Take a good look at your data before picking a format for it.


Conclusion: 
    If your problem doesn't need mixed content, then don't use XML.

Comments?

/Roger

[1] http://seanmcgrath.blogspot.com/2007/01/mixed-content-trying-to-understand-json.html

[2] http://lemire.me/blog/archives/2010/11/17/you-probably-misunderstand-xml/