If I want my iOS app to use a RESTful WebService that returns XML data, which APIs do I want to start learning?

I'd like to build in some weather functionality into my app and I'm going to be using the NOAA weather web service to retrieve the weather information. The NOAA website has a great deal of information on how the data should be requested and how the resulting data is structured. I'm new to iOS development, so I just need a little direction because I'm not sure which APIs I should be using to request and process this data. My questions are...

1. What's the proper way to request access to the user's location?
2. If the user allows access to their location, which APIs would I use to access it?
3. To 开发者_开发问答make an HTTP request to the RESTful webservice, which APIs should I use?
4. To process/parse the resulting XML data, which API's should I use?

And if anyone can suggest any good examples online that demonstrate any of this functionality, that would also be helpful.

Thanks so much so much in advance for your wisdom!

For location data, look into CoreLocation
http://developer.apple.com/iphone/library/documentation/CoreLocation/Reference/CoreLocation_Framework/index.html

For HTTP requests I like to use the ASIHTTPRequest class
http://allseeing-i.com/ASIHTTPRequest/

TouchXML makes it easy to work with XML data
http://code.google.com/p/touchcode/wiki/TouchXML

Just today, Luke Redpath posted a complete iPhone REST client he wrote. I can't vouch for it, I only saw today that it even exists. But Luke does good work, so I assume it's pretty decent.

See here: http://lukeredpath.co.uk/blog/some-code-that-i-wrote.html