[XML-SIG] Re: XML RPC proposal: Why XML?

Greg Stein (Exchange) gstein@exchange.microsoft.com
Wed, 15 Apr 1998 15:55:03 -0700

Dave's comment on readability is a big bonus. I designed (with a few others)
and implemented a protocol for MUDs to talk to each other. The protocol has
been in use for about three years now by hundreds and hundreds of MUDs over
that time. One of the biggest reasons that it was adopted, implemented, and
used was the fact that it was readable text rather than binary (we did allow
for binary to be used in the future, but nobody has bothered).

Another reason for XML over other text formats is the prevalence of common,
standardized tools for dealing with XML. For example, every Win32 machine
with IE4 on it has XML support builtin (msxml.dll). It's hard to find
another text processor that is widely installed.


-----Original Message-----
From: Dave Winer [mailto:dave@scripting.com]
Sent: Tuesday, April 07, 1998 7:16 AM
To: Andrew Kuchling
Cc: xml-sig@python.org; frontier-xml@scripting.com
Subject: [XML-SIG] Re: XML RPC proposal: Why XML?

Andrew, thanks for getting in touch!

We'll have a spec soon. This stuff is moving quickly and since we're
implementing as we go, there are brief outages as our focus moves around.
Should be a week at most before we have more details on the site.

In my opinion, the most important reason to use XML instead of a binary
format is readability. Our feeling was that the format would gain more
acceptance quickly if you didn't need special tools to discover the method
names, parameters and returned results. We learned, in our experience with
Macintosh interapplication communication that developers lose interest in
this stuff, or don't document their interfaces well enough. If the messages
themselves are in ASCII we stand a better chance of understanding how the
calls work. It's a low-tech tradeoff, easy to understand, and you burn a
few cycles on each call as the price for being understandable.

Further, once the bridges are working, we can optimize as necessary. We can
build a compatible network using XML encoding, bridge all the OSes,
environments and languages, and then optimize. But I strongly believe it
has to start simple if it's going to gain traction in the various

And finally, thank you again for getting in touch. Setting up the
communication links between the communities is the next thing to do. The
Python world is a strong one that we respect and want to work with.

Dave Winer

PS: I've cc'd this to our Frontier-XML list. Perhaps we could get one
person from each of our lists to join the other so we can stay informed on
progress each of us is making?

PPS: I also really want to talk about interfaces between scripting
environments and scripting languages. We want to run Python in our world
but don't want to do source integration. 

At 09:59 AM 4/7/98 -0400, you wrote:
>Good day!
>I'm the owner of the Python XML Special Interest Group, and was
>interested in your RPC over HTTP proposal.  It doesn't look very
>difficult to implement, once you've made the DTD, or at least a more
>complete informal spec available.  For examples, what are all the
>data types supported?  How are errors signalled?  Et cetera...
>	However, one thing I'm wondering about: there's already a
>binary RPC encoding from Sun, XDR (External Data Representation),
>described in RFC 1832.  This encoding would be more compact, and
>wouldn't require an XML parser to decode, since it would just be a
>matter of gluing bytes together.  XML is obviously useful for
>long-term data representation and storage; I have more difficulty
>seeing why it's worth the processing time for transient messages.
>Simply because it gives you introspective information about the types
>of things, perhaps?  (And most scripting languages are dynamically
>typed, so that's vital, but it could be added with XDR by sending type
>identifiers along with the data.)
>	BTW, I may forward your response to xml-sig@python.org, where
>this is being bounced around.  (Feel free to CC: your reply there, if
>you don't mind possibly getting entangled in a discussion.)
>A.M. Kuchling			http://starship.skyport.net/crew/amk/
>It is easy---terribly easy---to shake a man's faith in himself. To take
>advantage of that to break a man's spirit is devil's work. Take care of
>you are doing. Take care.
>	-- G.B. Shaw, _Candida_

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