Rule Builder > Technical Rule Language Reference > Tokens for the Condition Part of a Rule > there exists a

The token there exists a inserts an "exits condition", which is true when there is at least one instance of an object in the working memory. The rule will be fired once for all the objects that match the condition in the working memory. When you click this token and expand the square brackets, the following code is displayed:

 WHEN
  •  there exists a [ event ] <select a class> [ from <enter a value> ]
    
  •  [where]
    
  •  [such that]
    
  • The token there exists a is composed of the subtokens given in Table 24.3:

    Table 24.3   Subtokens for there exists a
    Subtoken 
    Function 
    [event]  Declare an event object. 
    <select a class>  Declare the name of a class. 
    [from <enter a value>]  Insert a from or in expression. 
    [where]  Insert attributes of the class and bind them to local variables. 
    [such that]  Insert tests on attribute values. 


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