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Re: "Binary XML" proposals

Al Snell wrote:

> But the binary format should be semantically identical to the text one, so
> it's just a matter of different code to handle it - there's no change in
> the fundamental communication of information, just it's a neater and more
> lightweight mechanism.

The savings to be realized through the use of a binary format are premised upon
parsing the XML text only once and thereafter passing around or storing the binary
encoded output. Such a mechanism demands that every user of that data expect, or
accept, the identical output of that parse--effectively, a canonical rendering. It is
only such unanimity which would permit every user to accept the product of a parse
performed by any of them. In the rapidly growing internetworked universe, it is
precisely that unanimity which we cannot reasonably expect, because the fundamental
premise of accepting node-to-node opacity as the price of universal node-to-node
addressability is the exchange that underlies the internetwork topology. It is our
good fortune that XML appeared just as the number of these mutually-opaque but
mutually-addressable nodes is furiously increasing. I argue that the reasonable
understanding of XML acknowledges that every use of an XML document begins with a
fresh parse of that document in the context of that use. That parse is not required to
instantiate XML as XML--the document itself is already that instance--but to
instantiate the particular objects which that specific use of the XML document expects
and requires. Because of the uniqueness of the process which requires them, and of the
unique circumstances at every execution of that process, the only way to effect the
precise objects required is to instantiate them afresh (which, BTW, every use of the
binary encoded XML representation would require anyway). The distinction is that XML
processing requires by its nature that what drives that instantiation be the parsing
of XML, which is to say the lexical handling and, from it, the unique sememic
interpretation of XML syntax. You may choose to drive that instantiation off of
something other than XML syntax, but it is not then XML processing, and what you lose,
most significantly, in doing that is the ability for the same text to be understood
and usefully processed at the same time as something very different, but
simultaneously the valid basis for a transaction between, utterly dissimilar users.


Walter Perry