ext .vs extLst: experiment

[MURATA Makoto]

Dear colleagues,

I did some experiment.  The result is indecisive, but here
goes.

1) @MustUnderstand

Is @MustUnderstand checked?

If and only if extLst is an application-defined extension element,
extLst/@MustUnderstand will be skipped.  Meanwhile,
ext/@MustUnderstand will be skipped no matter which of extLst and
ext is an application-defined extension element.

<extLst mce:MustUndestand="foo">....</extLst> where foo is not understood.

Experiment:

MS Office2007  reports an error for
extLstTest-MustUnderstand-NonUnderstood.xlsx, wnhich contains the
above.  But no error is reported if foo references to a understood
namespace (see extLstTest-MustUnderstand-Understood.xlsx).

When a MustUnderstand is used in a different element, the result is
same.  (See sheetViews-MustUnderstand-NonUnderstood.xlsx and
sheetViews-MustUnderstand-Understood.xlsx)

This result suggests that extLst is NOT an application-defined extension
element.

2) ACB

Is an ACB processed?

If and only if extLst is an app-defined extelem, extLst/AlternateContent
will not be processed.  Meanwhile, ext/AlternateContent will NOT be
processed anyway.

<extLst>
  <mce:AlternateContent>
    <mce:Choice Requires="foo">
    </mce:Choice>
    <mce:Fallback>
    </mce:Fallback>
  <mce:AlternateContent>
</extLst>

Experiment:

MSOffice reports an error for extLstTest-ACB.xlsx, which contains the
above.  This suggests aht extLst IS an application defined element.

If an ACB is used in a different element, it is replaced by the
content of an selected Choice or Fallback.  See sheetViews-ACB.xlsx
and sheetViews-ACB-saved.xlsx.

3) NonUnderstood elements and attributes

When there are nonUnderstood elements and attributes, are errors raised?
Are such elements and attributes retained?

Experiment:

In the case of sheetViews elements, nonUnderstood elements and attributes
are silently discarded and no errors are raised. This does not depend
on whether or not they are ignorable.

sheetViews-NonUnderstood-Ignorable-Saved.xlsx
sheetViews-NonUnderstood-Ignorable.xlsx
sheetViews-NonUnderstood-NonIgnorable-Saved.xlsx
sheetViews-NonUnderstood-NonIgnorable.xlsx

In the case of extLst elements, nonUnderstood attributes are
*retained* and no errors are raised. This does not depend on whether
or not they are ignorable.

extLstTest-NonUnderstood-Ignorable-Saved.xlsx
extLstTest-NonUnderstood-Ignorable.xlsx
extLstTest-NonUnderstood-NonIgnorable-Saved.xlsx
extLstTest-NonUnderstood-NonIgnorable.xlsx

This result suggests that extLst IS an application-defined extension
element.

Regards,

Makoto
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