Re: Unspecified #IMPLIED attributes in Java (was: Goals: XML ...)
At 16:32 18/12/97 +0000, Toby Speight wrote: >Peter> Peter Murray-Rust <URL:mailto:peter@u...> > >> In article <18.104.22.168.19971218152122.29672990@p...>, >> Peter wrote: > >Peter> Is it the question of the return value of a non-existent >Peter> attribute. IOW what does >Peter> >Peter> <!ATTLIST FOO PLUGH CDATA #IMPLIED> >Peter> >Peter> <FOO BAR="baz" XYZZY="" BLORT="six spaces"/> >Peter> >Peter> return for >Peter> String s = element.getAttval("PLUGH");// could be "", or null > >David has answered the original question (what is isSpecified() for in the >Java simple API?), but I thought I'd mention that DSSSL's attribute-string >function returns #f for PLUGH; the Java equivalent of this is of course, >null. I think this is the Right Thing to do; it's sometimes important to >tell the difference between <Fu bargh=""/> and <Fu/>. I agree that it is the Right Thing to do. If everyone else agrees it is the Right Thing to do I will be very happy. If 10% agrees and the other 90% don't know what we are on about, we need to make sure they can't Go Wrong :-) > >The first case is often used to mean a known, empty value; the second >to mean "not known" or "not applicable". > >Concrete example: I'm a rock climber, and I keep a record of all my >climbing in XML format. Climbs are defined as How exciting - I used to be (not a very good one). [...] > >climbs.xml> <climb grade="VD" stars="" style="2" >climbs.xml> with="&p-hkm;">Difficult Crack</climb> > >Here, the lack of stars is explicit - it's not a high-quality climb. >Whereas > >climbs.xml> <climb grade="D" with="&p-ejk;, &p-dmj;" >climbs.xml> style="l">King's Chimney</climb> > >is a climb in a part of Britain where the star system isn't used, and >so I omitted the attribute - even though it probably deserves a star >or two. Not according to MacInnes' star system; he gives it zero stars :-). Seriously, if we adopt this system then we should make every effort to promote it. One difficult area is in editors - how do you signal the difference between "" and null when entering a value in a box? You either have to get them to input NULL (yukk) or add another button for "IMPLIED" (Ugh). I'd like some other expert opinion on this. It's a tricky area if we get it wrong. 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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