如果我希望我的iOS应用程序使用返回XML数据的RESTful WebService，我想开始学习哪些API？

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...I'd like to build in some weather functionality