[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Inheritance and subtyping in OO languages
I've found a good reference to the 8 year old paper that made the distinction between inheritance and subtyping most explicit. The paper itself is not online, but this summary is quite good: "[CCHO89] and [CoHC90] propose an approach based on explicit interfaces and interface containment. In this system of object interfaces, one type is considered a subtype of another if some subset of its interface is identical to that of the second. [...] Hence in this system class-based inheritance is strictly a reusability mechanism for sharing behaviour between objects, not to be confused with subtyping. For example two classes may be equivalent as types, though neither inherits anything from the other. So class hierarchies are not the same as type hierarchies, although they may overlap. Object interfaces [as in Java, C++, etc. - Paul] clarify this distinction between interface containment (subtyping) and class- based inheritance and give insight into limitations caused by equating the notions of type and class in many typed object-oriented programming languages [such as Simula 67 - Paul]." http://progwww.vub.ac.be/prog/persons/kimmens/research/Introduction-to-OO.html The paper itself is called: "Inheritance is not subtyping" and is quite famous, but unfortunately predates the Web. Paul Prescod - http://itrc.uwaterloo.ca/~papresco "Journalism is good if you follow the rules. Don't allow the human rights groups to spoil your profession" - Col. Godwin Ugbo of the Nigerian military dictatorship xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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