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Re: "Binary XML" proposals

On Tue, Apr 10, 2001 at 11:36:22PM +0100, Al B. Snell wrote:
>On Tue, 10 Apr 2001, David Brownell wrote:
>> > As it stands, PNG and JPEG and so on all have their own internal
>> > mechanisms for seperating image metadata from compressed data and stuff -
>> > ways of compartmentalising data in the files. Wouldn't it be nice to have
>> > a standard way of storing that data? 
>> You mean there's a problem using XML text in the comment segments? 
>> Bizarre notion, to permit text unless it uses XML.
>No, I mean there's a problem in that it'd be nicer if the image dimensions
>and encoding parameters and comments and all lived in XML.
>The hack way is to embed the XML in something else (meaning it's not an
>XML file any more) with the binary part also embedded.

Why is this a hack?  Large amounts of XML contain large amounts of
text; it's hard to imagine a binary encoding of document-oriented XML
achieving any real benefits.  A sufficiently advanced encoding scheme,
such as BER for ASN.1, ultimately yields great pain in the programmer
(apologies to Olivier and the others who enjoy it ... I had to write
the protocol decodes with fairly hard real-time constraints, and I
*hated* it).  Or XDR for RPC ... I'll have nightmares, I'm sure, with
the memory returned now.

So, supposing that you want to be able to package up the images
associated with an XML document, why not package up the images
associated with an XML document?  Why not create a format that can
contain XML, instead of attempting to change the content of XML?  Such
things already exist, in some sense, of course, but then, binary
encodings of XML already exist as well (the ASN.1 mapping that
Olivier Duboisson's group is preparing, for instance).

>A nicer way would be to define an XML that can contain large blocks of
>bits without batting an eyelid (a property not easily provided in textual
>files!), then the image file can be an XML document the standard tools can
>play with to get the comments out.

Why?  Why is it nicer to stuff binary into XML (which is specifically
designed for text transmission), than to create a container meta format
to transport XML + binary?

Amelia A. Lewis          alicorn@mindspring.com          amyzing@talsever.com
I have spent nights with matches and knives, leaning over ledges, only two
flights up.  Cutting my heart, burning my soul.  Nothing left to hold.
Nothing left, but blood and fire.			-- Indigo Girls