At Webmonkey, the favorite technologies are, of course, those that inspire the most punning. So Java is way up there (all
those "brewing up" and "double tall" opportunities), as is HTML ("HTML is for Children" and "HTML and Back"), while topics like CGI and XSLT aren't really a whole lot of pun.
Thus I am extremely lucky to be allowed to write
about SOAP, one of the punniest technologies to come along since Unix.
And it's true: I feel lucky. So everybody scrub up, and let's get
started.
What Is It?
SOAP, or the Simple Object Access Protocol, is a protocol designed to help Web applications send messages to
each other. It's got a very simple, portable structure, based on XML,
and it can travel via HTTP, so it's lightweight and easy to implement, plus it's independent of language and platform. And thus the "Simple" part of the acronym, without which we'd now be learning about "OAP," which isn't nearly as puntastic.
Say this application you're writing needs to convert any European
Economic Community currency to euros, and vice versa, at the current
market rate. Your application can send a brief SOAP request to a server
that does the calculation and returns a response, also in SOAP.
Why is this neat? Well, maybe your application is written in Java, and
the server's doing its calculation in Perl. As long as they both use
SOAP, the transaction is perfectly clean and simple. Also, if your
application is running on a computer with Web access, the SOAP messages
can be sent via HTTP, through port 80. Using port 80 is nice because it
doesn't require any extra setup, and any firewall sitting in the way
assumes it's just more Web traffic, and lets it through, without the long
lines and cavity searches that often crop up if you set aside a
dedicated port. Three, SOAP is an open protocol (consult the W3C's Working
Draft of the SOAP 1.2 spec for more). There are a number of freely downloadable
SOAP client and server tools and libraries that can be bent to your
needs.
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