Currently all it does is inventory adjustments. It the future this may be expanded(which is why the name is a bit generic)
The format is:
CODE
<urn:PerformMultipleRequest>
<urn:UpdateInventoryRequestList>
<urn:Inventory ProductId="812">
<urn:QtyInStock Adjustment="true">10</urn:QtyInStock>
</urn:Inventory>
</urn:UpdateInventoryRequestList>
<urn:UpdateInventoryRequestList>
<urn:Inventory ProductId="813">
<urn:QtyInStock Adjustment="true">-1</urn:QtyInStock>
</urn:Inventory>
</urn:UpdateInventoryRequestList>
<urn:UpdateInventoryRequestList>
<urn:Inventory ProductId="814">
<urn:QtyInStock Adjustment="false">100</urn:QtyInStock>
</urn:Inventory>
</urn:UpdateInventoryRequestList>
</urn:PerformMultipleRequest>
This sets the inventory of product ID 812 to 10 above current, of product ID 813 to 1 below current, and ID 814 to 100. The adjustment attribute indicates if an adjustment is to be made or if a value is to be set directly. Omitting the Adjustment attribute is the same as setting it to false.