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Re: attribute order (RE: Syntax Sugar and XML information models)
Date: 3/29/2001 5:35:00 PM
Jonathan Borden wrote: > Simon St.Laurent wrote: > > Mike Champion wrote: > > >[...] Does anyone care about round-tripping the > > >specific syntax used in some instance, e.g. <empty></empty> vs <empty/>? > > >There was some discussion on SML-DEV once about using it to encode the > > >distinction between an element with the value [empty string] vs an element > > >with the value "null" ... but the fact that the distinction wouldn't > > >necessarily survive a round-trip with an InfoSet-compliant tool put that > > >idea to rest. > > > > If XML 1.0 had genuinely described only a syntax, I think the distinction > > between the two would be preserved. Since it defined a syntax with some > > processing notions behind it, and the Infoset people have codified those > > notions, I think those possibilities disappeared. > > > From a practical point of view that possibility disappeared when the SAX > interfaces and XPath was written. It disappeared long before that actually. Quoting The Handbook [*], p. 307: "An element has a start-tag, content, and an end-tag, but there are situations in which any one of those might not be there. [...] [T]echnically the content always exists, even if it is empty and loooks as if it isn't there." and p. 590: "NOTE - If the element was empty, ESIS does not indicate why it was empty; that is, whether it was declared to be empty [...] or whether it just happened to contain no data characters." If you consider a document to be a tree - which is the central idea behind SGML - there is no difference between a leaf node and a non-leaf node with no children. (If you think of documents as trees, the latter notion is almost nonsensical - a node with no children _is_ a leaf.) > Is something like that really worth going > back and changing a bunch of working code to handle this case? Not to mention changing the core conceptual framework on which all the code and specifications are based! --Joe English jenglish@f... [*] That's _The SGML Handbook_, copyright 1990 Charles Goldfarb.