XML and Using It With Whitespace

Chris Smith smith at interlog.com
Fri Jan 9 02:41:36 GMT 1998

On Tue, 6 Jan 1998, Tim Bray wrote:

> Date: Tue, 06 Jan 1998 18:56:52 -0800
> From: Tim Bray <tbray at textuality.com>
> Hmm, I'm failing to get some aspect of your problem.  Maybe I
> bypassed a message in which you explained it.  It is clear that
> *any* conformant parser must give you all the whitespace in the
> message.

The difficulty was not with insignificant whitespace, it was with
unwanted whitespace. For example, (old ground, I know, I'm sorry) if a
long line of text gets broken by changing a space to a lineend, then
message authentication will fail.

XML has done an admirable job with whitespace in element content, but
we were looking at a different problem. We wanted to try (where
possible) to rescue transport mechanisms, such as email, that
occasionally damage their content.

> Probably I'm missing something... what is the missing piece from
> your point of view? -T.

We were trying to save the world :-).

Notice I'm using the past tense?

In our conference call this morning, we finally decided we'd had
enough. Transport mechanisms that damage their content are broken.
Period. Fix the transport.

As a result, we have taken a different approach, one that draws rather
heavily on watching the parser work going on here. It essentially is:

- parse the document, using the DTD.
- generate a clean XML document (in UTF-16) from the parsed version
- run the authentication check on that

I'll post the definitive section of our spec in my next message.

Because the authentication is carried *inside* the XML document, the
whole document doesn't actually get authenticated. We authenticate any
one element (except, I suppose, the document element) which includes
an authentication of all content. You can include multiple
authentications, which may nest.

There are other complications, but I'd need to put in the whole spec.
Considering that XML essentially rescued our group from an encoding
stalemate, I'll post the press release (which I understand is coming
out on Monday.)

 Chris Smith                                          <smith at interlog.com>

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