Model representation of a reusable "expression" which can be referred to using %expression.expressionName in this domain definition.
Whether or not values passed through %Build() at runtime should be accepted as values for this parameter. If no value is specified at runtime,
valueis still used by default.
Name of the expression, which can be referred to using "%expression.name" onwards
Value of this expression. This can refer to other (previously) defined expression or domain class methods.