public interface ISemanticWrapperImplemented by nodes in the semantic tree which are not created explictly by the grammar. For example, the grammar generates BinaryExpression but we might programmatically create ConditionalExpression. During generation we need to know what specific class to use to locate the parselet which we use to process the value. This method lets us do that. The returned class will always be a subclass of the implementing class and must expose the properties required by the definition for the rule to generate properly.