Drools uses a Map instead of a SortedMap to accelerate the matching of patterns that have an equality relationship. Performance-wise this is the right decision most of the time, but if one wanted to accelerate matching of patterns such as

Person(age > 100)

having a sorted index could be beneficial. In a case like that the object in question must implement Comparable or be associated with a Comparator. This behavior could be turned on for a particular field with @-annotation in either the DRL or Java file.