You can only list a single tag (either for sub-tags or for objects).  Atmos is first and foremost an object store, not a database.  Generally speaking, if you require complex searching, then yes, you should put your metadata in a separate database and store the object identifier there.  The vast majority of customers do this.  However, many of our customers also asign one or two listable tags to their objects so they may be located by a 3rd party tool, for debugging, or just in case their primary database fails for some reason so they can re-associate the objects.  To my knowledge there is no current plan to add key-value searching as a feature of Atmos.
Hi, with java api I have uploaded an object (file1.txt) and set this listable user metadata:  customer=Company 1 typology=billing year=2013 number=123456  Can I retrieve objects researching for the value of the tag?  Example i want all objects where value of tag "customer" equals "Company 1"  It's possible?  Thanks
Atmos search by object metadata