This type of seismogram source allows several seismogram sources with the first one that has data for a given even-channel being used. It goes through each of the choices in the order given, and uses the first one that gives any available data. If no choice has data, then the result of the last datacenter is used (albeit the empty result). The example tries to get data from the BUD first and then POND if it isn't in the BUD.
<tryInOrder> <fdsnDataSelect> <name>Local Caching server</name> <host>myserver.myuniversity.edu</host> </fdsnDataSelect> <fdsnDataSelect> <name>IRIS server</name> </fdsnDataSelect> </tryInOrder>