Anatomy Of An XML-RPC Transaction

By Jon Udell

August 30, 1999

(Exploring XML-RPC :  Page 4 of 5 )

In this Article

Exploring XML-RPC Web components 101 The XML Dimension Anatomy Of An XML-RPC Transaction DCOM? CORBA? RMI? Why Not Just XML-RPC?

by a program. That's one of the great features of all Internet

software: the protocols (HTTP, SMTP, NNTP) are text-based and

therefore easy to understand and to manipulate in any programming

language.

Of course, that's also true for ordinary scripted CGI work, such as

our mindshare-measuring script. What's special about XML-RPC? Well,

consider the response that comes back when you send the wrong password

to the MailToTheFuture service using the normal CGI interface:

"Sorry! There was an error: Can't send you the cookie for 'yourname@yourmailhost.com' because the password is incorrect."

You can certainly teach your script to recognize and deal with

these kinds of responses, but it's going to be a fragile mechanism.

You're relying on free-form text patterns and, when they change, your

script will break. In the case of our mindshare-measuring script, for

example, a page redesign at either Yahoo or Alta Vista will very

likely force the script to have to recognize new patterns in the

output from these components.

Now consider the response that comes back from MailToTheFuture's

XML-RPC interface when you send the wrong password:

<?xml version="1.0"?>

<methodResponse>

<fault>

<value>

<struct>

<member>

<name>faultCode</name>

<value>

<int>4</int>

</value>

</member>

<member>

<name>faultString</name>

<value>

<string>The password is incorrect.</string>

</value>

</member>

</struct>

</value>

</fault>

</methodResponse>

Like the request, this response is well-formed -- and thus

automatically parseable -- XML.

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