If the user includes the gound squares beneath the character in a walk right rule, then the character will only walk when it is on ground. If the user makes a walk right rule that does not include these squares, then the character will be able to walk through the air. A very simple and effective way to infer intent is to include default behavior. However, defaults are not very powerful, since they can only make generic inferences. Overly intelligent defaults are perceived by the user as being inconsistent.
Creator uses defaults in many situations to make the process of creating rules easier.
In Creator, characters can have more than one appearance. For instance, there may be one appearance for facing left, and another appearance for facing right. The user must decide whether a rule should apply to just the current appearance of a character, or to all appearances. We have found that in the majority of cases, the appearance of the self character is important in the rule, while the appearance of other characters in the rule is not important. Therefore, by default, Creator automatically adds a test to each rule to require that the appearance of the self character matches the appearance in the rule.