MCE questions

[MURATA Makoto (FAMILY Given)]

Dear colleagues,

The more I think about the processing model of MCE, the more questions 
I have.   Here goes.

Q1. Suppose that an element is ignored.  Is anything in this element
allowed by MCE?  In particular, are (1), (2), and (3) (shown below)
allowed?

  (1) @mustUnderstand specifying a non-understsood namespace
  (2) non-understood and non-ignorable elements/attributes
  (3) Incorrect use of MCE elements and attributes

For example:

<U:foo xmlns:mce="http://schemas.openxmlformats.org/markup-compatibility/2006" 
     xmlns:U="http://understood.com/"
     xmlns:NU1="http://non-understood.com/one"
     xmlns:NU2="http://non-understood.com/two"
     mce:ignorable="NU1">
  <NU1:bar mce:mustUnderstand="NU2"/>  <!-- Example of (1) -->
  <NU1:bar>
      <NU2:hoge/>                                        <!-- Example of (2) -->
  </NU1:bar>
  <NU1:bar mce:Ignorable="1"/>                  <!-- Example of (3) -->
</U:foo>

where "http://understood.com/" is understood while neither
"http://non-understood.com/one" nor "http://non-understood.com/two" is
understood.

Q2: Also suppose that a Choice or Fallback is not chosen by the MCE
processor.  Is anything in this element allowed by MCE?  In
particular, are (1), (2), and (3) (shown in Q1) allowed?

For example:

<?xml version="1.0" encoding="UTF-8"?>
<U1:foo xmlns:mce="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:U1="http://understood.com/one"
    xmlns:U2="http://understood.com/two"
    xmlns:NU1="http://non-understood.com/one"
    xmlns:NU2="http://non-understood.com/two"
    mce:ignorable="NU1">
    <mce:AlternateContent>
        <mce:Choice Requires="U2">
            <U2:bar/>
        </mce:Choice>
        <mce:Fallback>
            <U1:hoge1 mce:mustUnderstand="NU2"> <!-- Example of (1) -->
                <NU2:hoge/>                                      <!-- Example of (2) -->
                <U1:hoge2 mce:Ignorable="1"/>          <!-- Example of (3) -->
            </U1:hoge1>
        </mce:Fallback>
    </mce:AlternateContent>
</U1:foo>


Q3: Is anything in an application-defined extension element allowed by
the MCE preprocessor?  In particular, is syntactically-incorrect use
of MCE elements and attributes allowed?

<extLst  xmlns:mce="http://schemas.openxmlformats.org/markup-compatibility/2006"> 
  <ext uri='http://purl.oclc.org/ooxml/spreadsheetml/versionTwoExtension'> 
    <v2:newContent 
        xmln:v2='http://purl.oclc.org/ooxml/spreadsheetml/versionTwoExtension'
        mce:mustUnderstand="1">                  <!-- Example of incorrect @mustUnderstand-->
        <mce:Choice Requires="3">                <!-- Example of incorrect Choice-->
              <mce:Fallback>                            <!-- Example of incorrect Fallback-->
                    <mce:AlternateContent/>       <!-- Example of incorrect AlternateContent -->
              </mce:Fallback>
        </mce:Choice>
    </v2:newContent> 
  </ext> 
  <ext uri='http://www.extension.com/versionOneExtension'> 
    <v2:moreContent xmlsn:v2='http://www.extension.com/versionOneExtension'> 
      … 
    </v2:moreContent> 
  </ext> 
</extLst>

Cheers,
Makoto