ISSUE-138: clarify usage of default namespace in EMMA

Issue 1: More clarity on default namespace on the emma:emma element (not the emma prefix from xmlns:emma but the default namespace on xmlns). The EMMA specification says that "Application markup MAY be declared in an explicit application namespace, or an undefined namespace (equivalent to setting xmlns="")" but doesn't go into what the meaning of doing this is or, perhaps more importantly, what the meaning of not doing this is. A number of XML tools will complain and fail if an EMMA document does not set the namespace but the interpretations end up using application specific XML elements. All of the examples in the EMMA specification do end up defining the xmlns attribute on the root element and point to http://www.example.com/example. What would the expected behavior be if this namespace was missing? I.e., is:

<emma:emma version="1.0"
xmlns:emma="http://www.w3.org/2003/04/emma"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3.org/2003/04/emma
http://www.w3.org/TR/2009/REC-emma-20090210/emma.xsd">
<emma:one-of id="r1" emma:medium="acoustic" emma:mode="voice">
<emma:interpretation id="int1">
<origin>Boston</origin>
<destination>Denver</destination>
<date>03112003</date>
</emma:interpretation>

<emma:interpretation id="int2">
<origin>Austin</origin>
<destination>Denver</destination>
<date>03112003</date>
</emma:interpretation>
</emma:one-of>
</emma:emma>

A valid EMMA document (this is the example from 3.3.1 but without the xmlns="http://www.example.com/example"?

Revised Jun 2 editor draft to make the xmlns= required:

Application markup MAYMUST be declared either in an explicit application namespace, or an undefined namespace by setting xmlns="".

** Still need to revise the schema.