Unformatted text preview: specification. The drawback is that if some property is leﬁ out of the constraint, there is a
no way user can make use of it. The requirements that they impose on subtypes are very
strong and raise a concern that it might rule out many useful subtype relations. To address this concern they have applied the methods to a number of examples. According to text book, subtyping is defined as, if T is a subtype of U, written T < : U, if a value of type T can be used in any context in which a value of type U is expected. Whereas, according to the Liskov & Wing paper, some constraints of T and U (pre, post and history rules) need to be satisfied.
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- Spring '10
- Dr. Thomas