The iOS library right now uses the AGFilterConfig for defining queries and filter options: https://github.com/aerogear/aerogear-ios/blob/master/AeroGear-iOS/AeroGear-iOS/pipeline/AGFilterConfig.h
We should see if using NSPredicate makes sense: https://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSPredicate_Class/Reference/NSPredicate.html