This writing is along the lines of Soap services. This is another question I see a lot floating around the net. When is it best to use NSXML event parser or Apple’s newer NSXML Tree Based XML Parser? The answer depends on the number of times you will need to get information from the xml document. In other words, will the software require multiple queries of the file to get information or is all of the information in the file going to be presented to the user at one time. The answer here is critical because the NSXML Tree parser can be very memory intensive as the entire XML is read into memory to form the tree to query. The NSML Event parser does not load the file into memory it simply reads the file line by line and sends event notifications to a delegate so that something can be done with the information. I learned this back when I created my TV listings app. The Tree based parser was really slooooow. Querying the XML document by Xpath or Xquery took a long time. One thing I realized is that my app did not need to make multiple queries to the document. It was much easier and much more memory efficient to use the Event parser to gather data and place into containers for later retrieval by the software. What kind of difference did this make. Well it went from 2 to 3 minutes to construct the data and present it to the user with NSXML Tree to 10 to 15 seconds with the event parser. If anyone needs any help with this area please feel free to email me.