| FeatureVariable
 A Feature marked as a Variable in the installation
 will exist even when a robot is turned off and on. 
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| GlobalVariable
 GLOBAL variables are available everywhere in a program. 
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| PersistedVariable
 PERSISTED means that the variable is stored with the installation. 
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| Variable  | 
| Variable.Type
 The variable type used to determine which type of variable this instance is. 
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| VariableException
 This exception is thrown if a Variable has an illegal name. 
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| VariableFactory
 This interface supplies methods to create variable objects. 
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