[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Inheritance/defaulting of attributes
Paul I really like your inheritance paper, but would like to suggest a minor change. Firstly let me pick up on the name question. Because of the preconceived ideas that programmers have about what inheritance and subclassing involves I would love to get away from these terms. I really liked the term >Environmental Acquisition defined in > http://www.cs.technion.ac.il/~david/Papers/Tech_Reports/lpcr9507.PS.gz >in: > http://www.cs.technion.ac.il/~david/publications.html > This fits in beautifully with SGML as it incorporates the concept of being able to use context to determine the meaning of elements, which is one of the great plusses of SGML. This fits in nicely with what has been done in HyTime and DSSSL to allow querying of context within groves. The one area of concern I have with your proposal is over the position of INHERITS. Unlike the other keywords you have proposed this defines the attributes to be associated with the following named parent rather than a mapping to be applied to the following element name. I would like, therefore, to distinguish this fact by placing it after the model group rather than before it. e.g. <!ELEMENT area EMPTY INHERITS (sizeable, has-href)> This would have the advantage that you could then combine TYPEOF and inherits: <!ELEMENT dog TYPEOF animal (puppies+) INHERITS (pedigree, kept-by)> >Architectural forms do not directly express the notion that element type A ISA subclass of element type B at the SGML parser level. Not at parser level, but at architectural processor level, where the architectural processor could be a spawned SGML parser working from the meta-DTD. Thats deliberate. >Since archforms do not have parser level subclassing, the parser cannot check subclasses for conformance as OO language parsers do. Nor can DTDs be checked for conformance to meta-DTDs. Again why presume it has to be done by a single parser? There may be good reasons for keeping these separate. >More subtly, I don't think the true subclassing relationship finds any direct expression in the archform concept at all. Rather archforms allow you to express that individual elements of type A ARE-ALSO-OF type B. This is the key - architectural forms are not subclasses, they are ways of identifying that processing relevant for a known class of objects are also relevent for this new class of object. They are about reusing existing knowledge/coding rather than about inheriting properties per se. This is the problem with using terms such as subclassing and inheritence to describe them. What architectural forms are about is Environmental Acquisition. ----------------------------------------------------------------- Martin Bryan, 29 Oldbury Orchard, Churchdown, Glos GL3 2PU, UK Phone/Fax: +44 1452 714029 E-mail: mtbryan@s... For more information about The SGML Centre contact http://www.sgml.u-net.com For more information about the European Commission's Open Information Interchange (OII) initiative contact http://www.echo.lu/oii/en/oiistand.html 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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