The root tag can use the UpgradeFrom and UpgradeTo attributes to control which furniture can be replaced with your furniture and which furniture your furniture can be replaced with. The attribute should have a comma separated list of furniture, e.g.
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The root tag can use the UpgradeFrom and UpgradeTo attributes to control which furniture can be replaced with your furniture and which furniture your furniture can be replaced with.
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<pre><Root Base="Server Rack" Thumbnail="BigServerRackThumb.png" UpgradeFrom="Server Rack, Tower Server, Small Server, Medium Server" UpgradeTo="Server Rack, Tower Server"></pre>
This furniture can be upgraded to any furniture that has UpgradeTo="Server" and UpgradeTo="Big Server", but it cannot be upgraded FROM furniture that has UpgradeTo="Server". This is to avoid upgrading a server that sits on the floor to a server that sits on a table, as the table would have to be created out of thin air.