At the onset of XML four long years ago, I commenced a jeremiad against
Standard Data Vocabularies (SDVs), to little effect. Almost immediately after
the light bulb moment -- you mean, I can get all the cool benefits of web in
HTML and create my own tags? I can call the price of my crullers
<PricePerCruller>, right beside beside <PricePerDonutHole> in my
menu? -- new users realized the problem: a browser knows how to display a
heading marked as <h1> bigger and more prominently than a lowlier
<h3>. Yet there are no standard display expectations or semantics
for the XML tags which users themselves create.
That there is no specific display for <Cruller> and, especially,
not as distinct from <DonutHole> has been readily understood to
demonstrate the separation of data structure expressed in XML from its display,
which requires the application of styling to accomodate the fixed expectations
of the browser. What has not been so readily accepted is that there should not
be a standard expectation for how a data element, as identified by its markup,
should be processed by programs doing something other than simple
display.
