one key or a whole bunch?

Hello,

I am looking for the most efficient way to use keys to
do the following.
My xml sample below:-

<SHOP>
<SPORTS>
..... <--- other stuff
.....
<SHELF_NO>4567</SHELF_NO>
.....
</SPORTS>
<LEISURE>
..... 
.....
<SHELF_NO>3344</SHELF_NO>
.....
</LEISURE>
<CLOTHES>
..... 
.....
<SHELF_NO>3344</SHELF_NO>
.....
</CLOTHES>
<GIFTS>
..... 
.....
<SHELF_NO>3344</SHELF_NO>
.....
</GIFTS>
</SHOP>

I need to get a count of all the groups of
<SHELF_NO>'s that are the same.
I need the output to be in the form (with the example
above):-

Shelf Groups   Number of Copies
0   0 <--i.e. no instance of no shelf number
1   1 <--i.e. 1 instance of just one unique shelf
number
2   0 <--i.e no instance of two shelf numbers the same
3   1 <--i.e. 1 instance where three shelf numbers
were the same
etc etc

So is the best way to have a key like: -
  
<xsl:key name="kShelf" match="SPORTS | LEISURE |
CLOTHES | GIFTS" use="SHELF_NO"/>

and a variable say

<xsl:variable name="vShelf"
                  select="SHOP/*[generate-id()
                                    =
                                    
generate-id(key('kShelf',
                                                     
SHELF_NO
                                                    
)[1]
                                                 )
                                    ]"/>

Then I get stuck as to how to iterate over them and
count the groups. 

Something like?

<xsl:for-each select="$vShelf">

<xsl:value-of select="count(key('kShelf', SHELF_NO))"
/> ??? just once or for all groups?
  
</xsl:for-each>

Any help gratefully received.

Thanks

Marina


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