Syntax
 aVariable.exists()
Semantics Returns true if aVariable is not null, otherwise false. See chapter NULL Values to read more about null values.
Substitutables aVariableCan be a variable or an attribute of an object. 
Examples
set b1 = x.exists();
set b2 = myObject.myAttr.exists();

Assigns the boolean return value of operation exists() to variable b2. Returns true if the attribute myAttr of object myObject is not null.

Example File (Builder project E2E Action Language/BaseTypes):

<your example path>\E2E Action Language\BaseTypes\uml\boolean.xml