[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Inheritance (was: Access Languages are Tied to Schemas)
Rick Jelliffe wrote: > The best idea I have some up with is the following: to allow a new keyword > #OTHER (or #ANY) > to be allowed in content models, to represent any one unambiguous element type. > This allows the creator of the original content model the ability to > declare points in content models which are publically available for extension > by derived element types (declared or undeclared). > > I currently think that any inheritance-based declaration system must presuppose > such explicit inheritance points. I think it is merely a matter of strong typing > and interface control. Strong typing and interface control are issues of subclassing, not inheritance. Inheritance is just a code reuse mechanism. Unlike subclassing, it does not allow more expressive DTDs to be created (which is, presuamably, what you are talking about). I think that we must keep these ideas separate in our mind if we are to make progress on either front. Their conflation is, (IMO) just a historical mistake driven by early compiler limitations and performance considerations that do not apply to SGML. Both concepts are useful in SGML, but they should be separate, just as they are in most modern OO programming languages (C++, Java, CLOS, Python, etc.), even those which conflate them in the syntax. I described the difference in: http://www.lists.ic.ac.uk/hypermail/xml-dev/9710/0077.html Anyhow, you can emulate OTHER using subclassing without a first class OTHER construct. <!ELEMENT CITATION (name, author, date, OTHER-CIT* )> <!ELEMCLASS OTHER-CIT> <!-- no constraints on subclasses --> <!ELEMENT URL (#PCDATA) SUBCLASSES OTHER-CIT> Now URLs can go in CITATONS after the date. Paul Prescod xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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