Pattern matching and dta abstraction are important concepts in designing programs, but they do not it well together. Pattern matching depend on making public a free data type mpresentaiion, while data abstraction depends on hiding the repreentaiion. This paper proposes the vdws mechanism at a means of reconc'dlng this conflict. A view allows any type to be viewed at a free data type, thus combining the clarity of pattern matching with the eiclency of data abstraction.