Perhaps the document should be stored in canonical form. See http://www.w3.org/TR/xml-c14n
I think I agree with Rod's opinion elsewhere in this thread. I guess the "philosophical" question is this: If 2 XML documents with different encodings have the same canonical form, or perhaps produce the same DOM, are they equivalent? Merlin appears to want to say "no", and I think I want to say "yes".
cheers
andrew
Merlin Moncure wrote:
Peter Eisentraut wrote:
The central problem I have is this: How do we deal with the fact that
an XML datum carries its own encoding information?
Maybe I am misunderstanding your question, but IMO postgres should be treating xml documents as if they were binary data, unless the server takes on the role of a parser, in which case it should handle unspecified/unknown encodings just like a normal xml parser would (and this does *not* include changing the encoding!).
According to me, an XML parser should not change one bit of a document, because that is not a 'parse', but a 'transformation'.
Rewriting the <?xml?> declaration seems like a workable solution, butit
would break the transparency of the client/server encoding conversion.
Also, some people might dislike that their documents are being changed
as they are stored.
Right, your example begs the question: why does the server care what the encoding of the documents is (perhaps indexing)? ZML validation is a standardized operation which the server (or psql, I suppose) can subcontract out to another application.
Just a side thought: what if the xml encoding type was built into the domain type itself? create domain xml_utf8 ... Which allows casting, etc. which is more natural than an implicit transformation.
Regards, Merlin
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