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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Re: [dsdl-comment] Re: Re: Re: DSDL: u
![Re: Re: [dsdl-comment] Re: Re: Re: DSDL: u](/images/get_stylus.gif) james anderson wrote: > I do not argue with the spec. I note that the recommendation specifies a notion which is untenable. In order to implement the > specification one must supplant or contradict its notion in some significant manner. This line of argument is vacuous and I've managed to avoid getting irritated by it for some 25 posts now but patience ran out. The namespaces rec defines a condition it calls "being in a namespace" and provides syntactic rules whereby element types and atribute names may be said "to be in a namespace". It notes explicitly that the namespaces defined in this document differ from the conventional (computer-science) set-theory-based usage. Similarly, the XML recommendation defines the term "type" and uses it in a sense that differs quite strongly from the "type" of variables in C programs, or the lead objects that used to be used in printing. HTML defines a "hyperlink" which is something quite different from the object of the same name in Ted Nelson's theory and (separately) in Mac Hypercard's implementation. Unless recommendations are to start creating synthetic nonsense names for the formalisms they describe, we are stuck with the current use of names with (hopefully) mnemonic value. It is a common but irritating error to assume that a name used in a formalism is the same as the common usage of that name in some other field. Elements with no prefix and no default in effect, and attributes with no prefix, are not in a namespace as the term is used in the formalism described by the Namespaces recommendation. A programming API which suggests anything different is simply an erroneous implementation. A set of related factors that can lead to confusion: - The empty string "" is in fact a perfectly good URI reference, meaning "the resource in which I appear" - it is impossible for the empty string "" to serve as a namespace name in the Namespace recommendation's formalism, as this empty string is a used as a signal to *undeclare* the default namespace - and it has been proposed to extend this facility to undeclare namespace prefixes as well. - it turns out that in a programming library, it is perfectly reasonable to use the empty string "" as a signal that no namespace is in effect. Note that it would also be perfectly reasonable to use a NULL or null string (in C or Java terms) or some other string that can't be a URI, e.g. ":". The use of "" for this purpose (which I helped argue into SAX against those who wanted to use null) is awfully convenient because it allows a bunch of common things to be based on string comparison operations. However it is confusing because it supports a fuzzy line of thought along the lines of 'since "" is the URI ref to the current document, obviously the unprefixed stuff is in the "default namespace" of the current document' which, while sweet on the mental tongue, finds no support in the namespace recommendation. -Tim 
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