1. A method of analyzing an initial ordered security rule-set comprising a plurality of rules, each rule comprising N≧1 extrinsic fields, wherein the rule-set is associated with at least one data structure specifying groups of extrinsic values characterizing at least one extrinsic field, the method comprising: upon specifying an extrinsic space constituted by atomic elements corresponding to extrinsic values characterizing an extrinsic field, partitioning said specified extrinsic space into two or more equivalence classes, wherein partitioning into equivalence classes is provided by mapping each atomic element of the extrinsic space over all groups of extrinsic values characterizing the at least one extrinsic field and comprised in the at least one data structure, and wherein each atomic element in said extrinsic space belongs to one and only one equivalence class and each equivalence class is constituted by one or more atomic elements of the extrinsic space that appear in same groups exactly; mapping said equivalence classes over the rule-set; using the results of mapping the equivalence classes over the rule-set for generating, by a processor, a logically equivalent security rule-set, wherein each of the respective rules in the generated rule-set comprises N−1 extrinsic fields; responsive to a request related to conditions specified in the rule-set with regard to a given group non-specified in the at least one data structure, providing a new partitioning into equivalence classes by mapping each atomic element of the extrinsic space over all groups of extrinsic values characterizing the at least one extrinsic field and comprised in the at least one data structure and over the given group; generating a new logically equivalent security rule-set; identifying equivalence classes corresponding to the given group; and analyzing the conditions specified in the new logically equivalent rule-set for each of the identified equivalence classes.