Interface Design Principle

Because hiding data representation means it can be easily changed without affecting the objects that use that data - for example, changing a stack's array representation to a list representation without affecting objects that use the stack

Explanation

Hiding data representation in an interface specification leads to a more maintainable design. Since the data representation is hidden, it can be changed without affecting any objects that use that data. For example, a stack's internal representation could be changed from an array to a linked list without changing the interface or any code that uses the stack through its interface. Operations to access and update data should be included; attribute definitions should not.