"XML is just syntax" versus "Use semantic markup" (Is this a paradox?)

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

Hi Folks,

I have often heard it said: "XML is just syntax."

I have equally often heard it said: "Use semantic markup."

How can XML be "just syntax" and also be "semantic markup"?

Is this a paradox?

Let me take a go at resolving this seeming paradox:

1. Tags are indeed just syntax.  They provide a mechanism for
structuring the data.

2. Tags are created by a specification, which define what each tag
means.  When constructing an XML document, there may be a choice of
tags, say <ABC> and <XYZ>, which may be used to wrap a particular datum
(item of data).  Suppose the specification gave tag <ABC> a general
meaning and tag <XYZ> a specific meaning. Compare:

    <ABC>datum</ABC>

versus

    <XYZ>datum</XYZ>

We say that the later is using "semantic markup."  This means: those
applications which have been implemented to understand the tag-set will
gain more information about 'datum' from the <XYZ> tag than from the
<ABC> tag.

Let me repeat the last sentence:

"... will gain more information about 'datum' from the <XYZ> tag than
the <ABC> tag." 

Hmm, sounds to me like the tags are providing more than just syntax.
The tags are providing information/meaning/semantics about 'datum'.

This paradox is unresolved in my mind.

Care to take a go at resolving this paradox?

/Roger