#18 Default namespace prefix problem

[Alamgir Farouk]

namespace { _"http://www.w3.org/TR/2003/CR-owl-guide-20030818/test#",
_ _"http://www.w3.org/1999/02/22-rdf-syntax-ns#", }

The second namespace overwrites the default namespace and causes ambiguity. Consider to change the default
namespace prefix "_" to something else.

why can the prefix not be null?

The empty string will be much better option if we have to solve this issue using this appraoch (not sure for now and I do not have a better idea for now). Of course it can be null also, but it'll require an extra check to verify that the handle is initialized. It'll be better practice if the NamespaceImpl constructor does not allow null.