Although several software modeling languages permit the representation of key aspects of physical entities, such as units, precision or measurement uncertainty, these aspects are not typically incorporated into their type systems. Therefore, operating with such properties is normally cumbersome and contrived. This paper shows how both data uncertainty and units can be captured in software models and naturally incorporated into their type systems. In particular, we present extensions of the UML/OCL type Real and define a set of operations on values of these new types. Furthermore, we show how they can be used in software models to carry out computations that consider measurement uncertainty and permit the detection of unit mismatches when trying to operate with their values.