Binary Data in XML

david at david at
Wed Sep 30 18:35:31 BST 1998

Tim Bray writes:

 > Suppose I wrote up a NOTE, should occupy less than one page,
 > proposing a reserved attribute xml:packed with, for the moment,
 > only two allowed values, "none" and "base64".  The default value is
 > "none".  If an element has xml:packed="base64" this means that

This sounds reasonably straight-forward, but I'd like a noun rather
than the adjective "packed".  Time rightly points out that
"xml:encoding" could cause confusion: are there any better suggestions 
out there?

 > This obviously couldn't retroactively become part of XML 1.0, but
 > if it went through a process and became a W3C recommendation, I bet
 > every parser author in the world would support it in about 15
 > minutes.

I don't know if the parser authors should worry about it -- how would
one deliver the binary information in the DOM or SAX, for example?  It
seems more likely that people would build support into the higher
interface layers like SAXON.

 > Base64 (a 4-for-3 encoding) wastes 33%, so I thought about perhaps
 > inventing Base128 (8-for-7) or maybe even a higher level to cut
 > down wasteage, but Base64 has the advantage that it avoids
 > UTF8/ISO-8859 confusion and I bet Mr. LZW will eat that 33%
 > anyhow...

Simplicity and ubiquity always win -- stick with Base64, since
everyone can already work with it.

All the best,


David Megginson                 david at

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