Hi all ACE has a notion of counting sets, like : XYZ is a product and it has exactly 3 parts. But as far as I know, it's not possible to say something about a cardinality not assigned to a value, like: If X is a product and it has a number of parts N then N is equal to the number of workers for X . The issue is similar for sentences involving maxima, minima, and sums. So the questions are: what are in ACE the possibilities to express notions like counting, maximum, minimum, summation. If nothing special , how difficult would it be to implement that ? Note that some Knowledge Representation langages like DLV have a formalism for that : <a href="http://www.dlvsystem.com/dlvsystem/html/DLV_User_Manual.html#AEN814" target="_blank">http://www.dlvsystem.com/dlvsystem/html/DLV_User_Manual.html#AEN814</a> N3 also has extensions . -- Jean-Marc Vanel Consulting, services, training, Rule-based programming, Semantic Web <a href="http://jmvanel.free.fr/">http://jmvanel.free.fr/</a> EulerGUI, a turntable GUI for Semantic Web + rules, XML, UML, eCore, Java bytecode +33 (0)6 89 16 29 52 -- +33 (0)1 39 55 58 16 ( we rarely listen to voice messages, please send a mail instead )