Test1.sadl

 uri "http://sadl.org/Test1.sadl" alias Test1.
 
 PhysicalThing is a class,
 	described by weight with values of type UnittedQuantity,
 	described by density with values of type float.
 	
 LivingThing is a type of PhysicalThing,
 	described by dateOfBirth with values of type dateTime,
 	described by age with values of type float.
 	
 Mammal is a type of LivingThing,
 	described by child with values of type Mammal.
 	
 Person is a type of Mammal.
 child of Person only has values of type Person.
 
 Pet is a class, described by caredFor with a single value of type boolean.
 owns describes Person with values of type Pet.
 
 External subtractDates(dateTime t1, dateTime t2, string u) returns float : "http://sadl.org/builtins/subtractDates".
 
 Rule AgeRule: if p is a LivingThing then age of p is subtractDates(now(), dateOfBirth of p, "y"). 	
 
 Rule AgeRule2: if p is a LivingThing then age of p is Test1:subtractDates(now(), dateOfBirth of p, "y").