3 Minor issues spotted

All,

During my previous exercise I spotted a few little things, as follows:

DataContext::setMapping (in DOMString prefix, in DOMString iri);
Perhaps could be
DataContext::setMapping (in DOMString prefix, in IRI iri);


Perhaps these two methods could have their signatures aligned (predicate 
- probably tying in with the above, all DOMString or all IRI):

DataStore::filter(in Object? subject, in optional IRI? predicate
DataParser::iterate(in Object? subject, in optional DOMString? predicate


DocumentData has the createParser( type , store ) method, but DataParser 
has no constructor which accepts a type, or any way of setting the type.

Best,

Nathan