My question is. the users searches for items based on taxonomy field. suppose you have a MMS Field with name "departement" which can get value (IT, economy, ...). after a while the client wants to change the name of its IT departement to "SUPPORT" departement, so we need to change the MMS data. and all new documents will get "SUPPORT" as value for departement field. Now the client wants that if you search for IT or SUPPPORT will get same result (all documents that have IT or Support for its deparement taxonomy field). is it possible? thanks
If I understood the scenario correctly, you have TERM SET called Department that contains TERMS like IT, Economy.
In this case you could create new term inside the term set "Department", and name it "SUPPORT". Then you should merge the IT term to the new "SUPPORT" term.
Note! This will remove term IT, so you can no longer use IT when you create new documents. Instead it will make IT as a label for term "SUPPORT", meaning all new documents you can only tag with "SUPPORT", but all old existing documents will still retain IT. So if you would then search for "SUPPORT" department documents, you would get both new ones with "SUPPORT" and old ones with IT defined.
It might be good idea to test merging with some test terms and term sets so you can be sure this suggestion doesn't have any drawbacks in your case.