xml-dev - RE: Notations

[Ronald Bourret <rbourret@ito.tu-darmstadt.de>]

Michael Kay wrote:

> > From: W. Eliot Kimber
> > Remember that notations do not affect the *parsing* of the data, only 
its
> > semantic interpretation.
>
> If that is so, I am back to square zero in my understanding of notations!
>
> For example, I thought that if I wanted to put MIDI data in an XML 
document,
> I would use notations to the indicate the fact. But I can't semantically
> interpret MIDI data (or even hear the music) before I've parsed it. The
> notation is surely there to tell me that it's MIDI, not that it's 
Vivaldi.

I think what Eliot means is that a generic parser does not treat the 
notated (notationized? annotated?) data any differently.  (In fact, a 
non-validating parser might not even know that it carries a notation.)  The 
parser parses the data in the same way it parses any other character data 
and passes it to the application.  It is then up to the *application* to 
interpret the data according to the notation.

For example, assuming MIDI data is binary, it might carry two notations. 
 The first would indicate that it is base64-encoded -- remember that this 
is still character data -- and the second would indicate that it is MIDI 
data.  Based on the first notation, the application would pass the 
character data to a base64 decoder to translate it to binary.  Based on the 
second notation, the application would pass the now-binary data to a MIDI 
application, which could play it for your enjoyment.

-- Ron Bourret


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