Define price expectation elasticity of demand?

Expectation elasticity of demand mean if in future the price will rise then in present the demand of that comm. will fall i.e elasticity will be +ve.. n vice versa..., RELATIONSHIP OF EXPECTION OF PRESE WITH THAT COMMODITY Expectations about future price rise or fall is directly related with present or a recent demand i.e if prise rise in future, the demand will rise 4 that comm. n vise versa....