Function notation for XML data fields

Instead of using a special notation that is convenient for most of the cases, you may use a function notation for accessing function. Find is a system function of the following signature:

Find: XML*string*Map<string, string> -> XML

This function can be used in the same way we send messages, like item.find("po:quantity", ns), where ns is defined as:

val ns = map{
"po" : "http://example.com/po",
"aa" : "http://example.com/po",
"" : http://example.com/po /* default namespace */
};

The advantage of this approach is that it takes the namespace information explicitly. If implicit namespace context is not appropriate, then you may use this approach.