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Jonathan Robie wrote:
> Does anybody really believe that XML is just UnicodeWithAngleBrackets, or is
> that hyperbole?
An XML *instance* is, in fact, just UnicodeWithAngleBrackets. It is only in
parsing an instance, and in instantiating some data structure on the output of
the parse, that elements, attributes, etc. are apprehended and reified in some
sensible way for the use at hand.
> Here's a view that I might call the "Only Structure" view: XML, like any
> language, has a surface syntax and associated semantics. "Unicode With Angle
> Brackets" describes the surface syntax, and the BNF in the XML Recommendation
> tells how to parse this syntax and what structures it expresses. The labelled
> structures expressed by an XML document are the
> semantics of the document.
As an XML *instance* is just UnicodeWithAngleBrackets, the instance manifests
only surface syntax. Semantics, in this case as in all others, are elaborated
from text by the operation of process. They do not inhere in the instance, nor
could you point out their locus there. The BNF productions of the Rec calibrate
a proper XML parser in its job of determining conformance of an instance to the
Rec. If that parsing is not terminated by draconian error handling, some
labelled structures (not *the* labelled structures, if by that you imply some
single canonical set) elaborated from that processing of that text instance are
instantiated on the output of the parse, and those structures may indeed be said
to embody one possible set of semantic outcomes from the processing of that
document.
Respectfully,
Walter Perry
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