[George Mitchell]
Even granting that a lot of people use XML for a lot of things and
that parsers are widely available, what positive reason is there to
use it for this particular application when far simpler solutions are
available?
That's just my point. A whole parser written just for SPFv1 is not a
*simpler* solution. Having a Python or Perl script that needs to be
called by a MTA-specific filter is not simple or efficient in many
implementation scenarios. And everyone knows Perl really sucks
syntactically (that's white it's being re-designed from almost scratch).
With XML as part of SPFv2, a developer implementing SPF for their MTA or
MUA (commercial or free) can simply use the XML parser their development
environment already has, and build only the rejection logic. These
widely-used XML libraries will be, for the most part, efficient and free
of stack-and-buffer overflows, something which cannot be said of a
re-implemented SPFv1.
Also, the SPFv1 language has a lot of underlying complexity. People even
talk about Turing-completeness. Re-implementing a SPFv1 parser may be
equivalent to writing a (simple) compiler. Do we want to force
implementers (commercial or open) that want to have control of their own
SPF to write a compiler just to use SPF? That's a big impediment to
adoption.
Whatever... SPF will need to be re-implemented a large number of times
on a large number of platforms if it is widely adopted. The reference
code cannot be used for everything. Does everyone use the free reference
C code provided by ANSI when doing AES encryption? Do we all still use
sendmail? There were "simple" solutions already available for AES and
SMTP... but look what happened.
But I would imagine that, of the total amount of data which flows
across the internet in all protocols, the amount which is expressed
in XML is vanishingly small. Certainly no existing part of the DNS
and SMTP protocols require the use of XML. I don't see any XML on
www.amazon.com or www.ebay.com or www.imdb.org.
First of all, most internet traffic is HTTP, transporting HTML. And HTML
compatible with the more recent W3C standards is XHTML, which is in fact
XML with a specific standardized schema. So I think you're probably
wrong: the majority of traffic on the internet *is* XML with a
standardized schema, or a slight syntactic variation thereof (HTML v4
and older).
See: http://www.w3c.org/MarkUp/#recommendations
Secondly, Amazon.com and eBay almost certainly use XML in their back
office data exchange. They do not appear to use XML+XSLT to generate
their web pages, but neither do I at the moment. Like everyone else I
have a crapload of stuff on my site that I don't want to convert. This
situation doesn't in any way diminish the utility or future of XML.
Regards,
Ryan