[xsl] dynamic grouping of tabular data; one or two transformations?

[Dan Diebolt <dandiebolt at yahoo dot com>]

I have a tablular set of data:

   A B C D
   0 0 0 0
   0 0 0 1
   0 0 1 0
   0 0 1 1
   0 1 0 0
   0 1 0 1
   0 1 1 0
   0 1 1 1
   1 0 0 0
   1 0 0 1
   1 0 1 0
   1 0 1 1
   1 1 0 0
   1 1 0 1
   1 1 1 0
   1 1 1 1

represented in XML as follows:

<root>
 <row> <A>0</A> <B>0</B> <C>0</C> <D>0</D> </row>
 <row> <A>0</A> <B>0</B> <C>0</C> <D>1</D> </row>
 <row> <A>0</A> <B>0</B> <C>1</C> <D>0</D> </row>
 <row> <A>0</A> <B>0</B> <C>1</C> <D>1</D> </row>
 ...
 <row> <A>1</A> <B>1</B> <C>1</C> <D>1</D> </row> 
</root>

I need to produce various grouped and indented views
of this data on demand. For example, if I group on {A} 
I would like this output:

  A B C D
  0 0 0 0
    0 0 1
    0 1 0
    0 1 1
    1 0 0
    1 0 1
    1 1 0
    1 1 1
  1 0 0 0
    0 0 1
    0 1 0
    0 1 1
    1 0 0
    1 0 1
    1 1 0
    1 1 1

If I grouped on {A,B} I would like this output:
  
  A B C D
  0 0 0 0
      0 1
      1 0
      1 1
    1 0 0
      0 1
      1 0
      1 1
  1 0 0 0
      0 1
      1 0
      1 1
    1 0 0
      0 1
      1 0
      1 1

And if I grouped on {A,C} I would like this output:
    
  A C B D
  0 0 0 0
      0 1
      1 0
      1 1
    1 0 0
      0 1
      1 0
      1 1
  1 0 0 0
      0 1
      1 0
      1 1
    1 0 0
      0 1
      1 0
      1 1

And just for completeness, if I grouped on {} I would like
this output:
    
   A B C D
   0 0 0 0
   0 0 0 1
   0 0 1 0
   0 0 1 1
   0 1 0 0
   0 1 0 1
   0 1 1 0
   0 1 1 1
   1 0 0 0
   1 0 0 1
   1 0 1 0
   1 0 1 1
   1 1 0 0
   1 1 0 1
   1 1 1 0
   1 1 1 1
   
For any specific grouping, I can define keys and apply
Meunch's technique. But I would like the XSLT to apply to any
tabular arrangement of data not just one with specific element
names (ie <A>, <B>, <C> or <D>). So I would like to a parameter
named "GroupBy" with values like "A", "A,B", "A,C" or "" to
define the desired table grouping. All of the above examples
would be rendered as html tables with empty cells for the
grouping and indention shown here for GroupBy="A,B"

<table>
 <tr><th>A</th><th>B</th><th>C</th><th>D</th></tr>
 <tr><td>0</td><td>0</td><td>0</td><td>0</td></tr>
 <tr><td> </td><td> </td><td>0</td><td>1</td></tr>
 <tr><td> </td><td> </td><td>1</td><td>0</td></tr>
 <tr><td> </td><td> </td><td>1</td><td>1</td></tr>
 <tr><td> </td><td>1</td><td>0</td><td>0</td></tr>
 ...
 <tr><td>1</td><td>0</td><td>0</td><td>0</td></tr>
 ...
 <tr><td> </td><td> </td><td>1</td><td>1</td></tr>
</table> 

So here is my question to the list: Is it possible to do this
with *one* stylesheet transformation? I can't see a way to generate
the required grouping keys dynamically. My thinking is to first
generate a stylesheet with the required key definitions and essential
transformation code and then transform the original XML source 
with this generated stylesheet:

  xsl2 = xml.transformNode(xsl1);
  html = xml.tranformNode(xsl2);
  
Any ideas would be appreciated. Thanks.

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