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David Megginson wrote: > Perhaps I'm a little confused, but I cannot see how the fact that a > schema language itself happens to be object oriented allows you to do > object exchange in XML (it doesn't hurt, but how can it help?). > > I've been confused before, so there's no need for panic. I'm not entirely sure whether or not I am confused myself. Let me give this a crack, and I'm sure someone will be happy to tell me why I am wrong. :-) Let's say I have an arbitrary object structure that I want to serialize and send down the pipe. Serializing a bunch of object attributes in XML is a no-brainer, and representing arbitrary references between objects is also fairly trivial if something like XLink is used (and we need XLink, there's surely no controversy about this). The aspects of object-oriented design that are missing are then inheritance and polymorphism. This is why an object-oriented schema language is needed: to do this properly I should be mapping each of my object classes to a specific element type, and I need to be able to say that a given element type extends a base type if this type of relationship is present in my original object schema. Rich data types are also needed although this doesn't have to do with object-orientation per se. Polymorphism is about behavior and should be implemented in schema-aware tools. I honestly feel that XML provides all the tools to do what RDF is trying to do, without an additional syntactic layer. What is missing from the picture is a mechanism for modelling object structures according to object-oriented principles, and this is why an OO schema language is necessary. The only other thing the RDF brings to the game is that it turns relationships into first-class objects that can be referenced as well, but I don't know any OO language that enables this without modelling it specifically (i.e. creating an object to represent a reference), and this can be done in an analogous way in XML as well. If I may, let me turn your question on its head: what about an XML Schema approach doesn't let you do object exchange in a satisfactory manner? Matthew 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/ and on CD-ROM/ISBN 981-02-3594-1 To unsubscribe, mailto:majordomo@i... the following message; unsubscribe 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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