SOAP is a protocol that passes XML over HTTP......it basically allows client apps to access data from remote servers.
Applescript has some tools to make it easy....if you want to use applescript, but Cocoa really doesn't. You have to hard code every function in a wrapper library to make the HTTP call, get the parsed resposnes, etc
In Microsoft.NET, you add a "Web Reference" to your project, it scans the WDSL webservice description file on the internet to figure out what functions are there, and then builds a C# class that acts like its a local peice of code. You just call the functions natively from your program, and you'd never know you are talking to a remote server. If the server program changes, one click in your client project updates that stub-proxy file to the newest WDSL, click compile and bam, you have access to the latest and greatest functions from the server.
With Xcode......you really have to do alot of work by hand. We have a web service with thousands of functions to access our ecommerce system, we want to make a Mac OS native version of our client, but the shear amount of time spent making/maintaining a proxy stub in Xcode by hand would be more than the amount of work porting the user interface. I'm really hoping they automate this!