Re: Inheritance/defaulting of attributes
Thanks Eve, At 18:16 04/10/97 -0400, Eve L. Maler wrote: >Inheritance/defaulting of attributes is a quite common thing in SGML (and >so presumably it will be common in XML). In fact, it's common enough that >a lot of people wish that SGML offered an attribute default value of >#INHERITED, as a more specific form of #IMPLIED. In some DTDs, I've >defined a parameter entity %inherited; that resolves to #IMPLIED, as a kind >of self-documentation of intent. > >I think it might get a little tricky, though, to nail down precisely what >the defaulting behavior should be if it's formalized in XML. When you >inherit a value from an ancestor, the attribute name is assumed the same >across both element types. But should they have the same declared and Yes - I agree. In XLL EXTENDED has (essentially) the same attributes as its child LOCATOR. I assume this is so that LOCATOR can inherit them from EXTENDED, rather than that EXTENDED actually needs them itself? [Please disabuse me if not - but I couldn't see an *obvious* separate use for, say, ACTUATE on EXTENDED other than to pass it to its children.] My own case is worse in that I have defined <!ELEMENT LIST ANY> since its role is simply to act as a container. Therefore *with a DTD* it would have to anticipate all the attributes of its children and those that it might wish to pass on to them. Without a DTD [more accurately, without wishing to validate the whole document against a single DTD] this is less of a restriction, but there still has to be a non-prose mechanism to pass the attributes on to the children. (Just as we have XML-ATTRIBUTE for mapping, we could ask the ERB for some inheritance mechanism :-) >default types? Is it an error if they don't? In fact, what this comes >down to is needing some sort of agreement over what attributes are "the >same," even though they're on different element types. (Hmm, a subject >that has been broached in the namespace discussion on the SIG list >recently...) An alternative - which I have only just read - could be the mechanism in the RDF spec (I assume this is public now and can be discussed on this list?). Since one can define a relationship between nodes, it would be possible for this list to suggest (or define) such relationships. I am not sure how generic this is, or whether it has to be done for each instance... P. > Peter Murray-Rust, Director Virtual School of Molecular Sciences, domestic net connection VSMS http://www.nottingham.ac.uk/vsms, Virtual Hyperglossary http://www.venus.co.uk/vhg 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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