Polymorphic Substitutability
      A synonym for LiskovSubstitutionPrinciple, but with a wider application. It applies not only to objects and classes, but to all entities that may be substituted for each other.
This includes:
        - Use Cases ("Buy Gas With Credit Card"  "Buy Gas")
        - Relationships (Composition  Aggregation  Association)
        - Others 
         
      
      Programmers, for example ;-)