[erlang-questions] Newbie training project proposal
Fri Sep 14 22:15:49 CEST 2007
On Tuesday, September 11, 2007, Joe Armstrong wrote:
> Do protocol designers turn off their brains when they design protocols?
> I see a lot of the following:
> - text protocols with are "easy" to understand and parse
> (false - most text protocols are inadequately specified)
One advantage of text protocols is that you can telnet to a port and do a
transaction manually. I'm thinking SMTP and HTTP here as examples. I have
on occasion had to send email without a mail client handy, so I just telnet
to port 25 of my mail server and type in the SMTP commands. Similarly, I
have had occasion to need a web page without a browser handy: I just
telnetted to port 80 and typed in my request.
STOMP is very HTTP-like. We'll be able to interact with the STOMP server
with nothing but telnet and a keyboard.
> - XML protocols
> (crazy - did anybody think how long it would take to parse this crap)
I agree with you wholeheartedly on this one. It's convenient for XML shops,
but as a basis for a protocol that might be used by multiple organizations,
it's a waste of resources. Non-XML shops end up having to do a bunch of
string manipulation, regexp searches and the like to manage XML, which is
awkward, buggy, and annoying.
> The two most obvious methods for building protocols are:
> - define a packed bit-byte-word structure appropriate to you needs
> - use serialised lisp S expressions, or Erlang terms (whatever)
> Are rarely used.
Agreed. I probably prefer S-expressions as the most generic. Even though
they are very Lispy, they are ridiculously easy to parse in any language.
Erlang terms are up there with JSON: they are kind of locking you into a
technology, but they're not too difficult (or verbose) for
of having to handle external DTD's, matching closing and opening tags,
handling attributes and namespaces, and so on.
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