Mapping Values.

I have an xml of the form

<root>
<bldg loc=3D3D3D"abcd" subloc=3D3D3D"abcd" />
<bldg loc=3D3D3D"xxxx" subloc=3D3D3D"yyyy" />
<bldg loc=3D3D3D"aaaa" subloc=3D3D3D"aaaa" />

<addr bldgloc=3D3D3D"aaaa" bldgsubloc=3D3D3D"aaaa" />
<addr bldgloc=3D3D3D"xxxx" bldgsubloc=3D3D3D"yyyy" />

 </root>

I have to convert it to
<root>
<bldg loc=3D3D3D"1" subloc=3D3D3D"1" />
<bldg loc=3D3D3D"2" subloc=3D3D3D"2" />
<bldg loc=3D3D3D"3" subloc=3D3D3D"3" />

<addr bldgloc=3D3D3D"3" bldgsubloc=3D3D3D"3" />
<addr bldgloc=3D3D3D"2" bldgsubloc=3D3D3D"2" />

</root>

So for this purpose I want to map some strings to some values that can be
used later. Like when I map bldg block in input to bldg block in output I
want to map the attributes to a number and then use the same when mapping
addr tags.
How shud I go about doing it ?


Amal.