Quering datasets

Hi all,

I am a new user and have studied Thredds in order to build an 
infrastructure for registered several opendap servers, distributed among 
differents sites,  in catalog. Once they are registered, I want to query 
which servers have data on a certain range longitude/latitude for the 
temperature variable, for example. This is possible?

Firsly, my plan is register all interesting opedanp server. Next, I 
could submitt queries (through DQC) as which servers (or datasets) has 
data on a certain range longitude/latitude for the temperature variable. 
The meta-attributes are automatically extracted from das/dds or I have 
to define them?

Thanks,

David