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At 10:05 AM -0500 3/13/03, msc@m... wrote: >I was thinking about this as well. > >If prefered, you could include some representation of the schema within the >compressed format. This would provide all the informatin needed for >producing the orginal instance, assuming you know the proper algorithm. >This would make things more like the tradtional gzip scenario, where the >replacement dictionary is included in the compressed file, and it's assumed >that you know the decoding algorithm. There are some XML compression schemes that do this. I consider those non-lossy. >The difference is that the schema based approach uses one set of information >to encode/decode an entire class of instance documents. Whereas in >something like gzip, you need a custom-made replacement dictionary for each >file you compress. So in a schema based approach, you realy only need to >deploy the schema once, rather than every time you send the compressed >information. This I don't believe. The fundamental flaw here is 1. Documents of interest have schemas 2. Documents of interest reliably satisfy their advertised schemas. These flawed premises underlie a huge amount of XML theory. Neither of them matches XML practice. Any satisfactory compression scheme must be prepared to handle invalid documents losslessly. -- +-----------------------+------------------------+-------------------+ | Elliotte Rusty Harold | elharo@m... | Writer/Programmer | +-----------------------+------------------------+-------------------+ | Processing XML with Java (Addison-Wesley, 2002) | | http://www.cafeconleche.org/books/xmljava | | http://www.amazon.com/exec/obidos/ISBN%3D0201771861/cafeaulaitA | +----------------------------------+---------------------------------+ | Read Cafe au Lait for Java News: http://www.cafeaulait.org/ | | Read Cafe con Leche for XML News: http://www.cafeconleche.org/ | +----------------------------------+---------------------------------+
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