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>>However, there are problems anyway because a class that implements the DOM >>Node interface in JDK 1.4 won't compile under JDK 1.5. What's at issue here is the difficulty of modifying interfaces in general, but I don't think the problem is quite as insurmountable as Dr. Kay does. Briefly we have two versions of the same interface, version 2 and version 3. Version 2 has methods A and B. Version 3 has methods A,B,C, and D. If we use version 3 in a system that expects version 2, then all the version 2 implementations will have methods A and B but not methods C and D, which are required to implement the interface. This is a compile-time or runtime error depending on various factors. The saving grace is that there's usually nothing to prevent a version 2 implementation from also providing the methods required by version 3, even though it isn't required to in a version 2 system. In this case, the Saxon classes could add the extra methods required by DOM Level 3 because the DOM Level 2 methods are a minimal set, not a maximal set. In other words a typical class that implements the DOM Node interface in JDK 1.4 won't compile under JDK 1.5 because it will be missing new methods added in DOM3. However, I think this could be repaired without breaking Java 1.4 compatibility. Am I missing anything? Is there anything more incompatible than additional methods like a method signature change to worry about? -- Elliotte Rusty Harold elharo@m... XML in a Nutshell 3rd Edition Just Published! http://www.cafeconleche.org/books/xian3/ http://www.amazon.com/exec/obidos/ISBN%3D0596007647/cafeaulaitA/ref%3Dnosim
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