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> From: John Cowan [mailto:jcowan@r...] > Sent: Saturday, March 23, 2002 5:33 PM > To: Julian Reschke > Cc: michael.h.kay@n...; 'Joshua Allen'; 'Rick Jelliffe'; > xml-dev@l... > Subject: Re: MSXML DOM Special Chars Less Than 32 > > > Julian Reschke scripsit: > > > Some of the requirements are: > > > > - the format of strings that *can* be represented as XML > characters doesn't > > change > > - non-XML characters must be ignored by implementations not knowing the > > escaping mechanism > > Those requirements are impossible. An escaping mechanism naturally > requires an escape character (which means that the format of strings > containing the escape character *must* change), and the only way > for an escape-blind system to ignore the escape is for escaped > characters to be represented by the null string. > If the escapes are elements, that makes the matter even worse, > since escape-blind systems will see violations of the schema. Why impossible? You just mentioned a format that fulfills the requirements (mixed content, using special elements to represent the offending characters): here we have a <ctl:bel xmlns:ctl="..." /> character. If there's an *additional* requirement that the format may not affect validation, then there'd be still the possibility to use PI-based escapes: here we have a <?ctl-bel?> character. However, I'm not sure that this requirement really exists (it certainly doesn't for SOAP and WebDAV). (it would be great if this discussion would lead to a common approach that could be applied to multiple protocols / XML formats).
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