Unspecified #IMPLIED attributes in Java (was: Goals: XML ...)
Peter> Peter Murray-Rust <URL:mailto:peter@u...> > In article <220.127.116.11.19971218152122.29672990@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/>. 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 climbs.dtd> <!ELEMENT climb (#PCDATA)> climbs.dtd> <!ATTLIST climb climbs.dtd> grade CDATA "" climbs.dtd> stars CDATA #IMPLIED climbs.dtd> style (l|2|al|s|tr|mt) #IMPLIED climbs.dtd> with CDATA #IMPLIED climbs.dtd> > Note the "stars" attribute, which is used for a climb's star rating (an indication of quality). An instance looks like 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. I would not want these two values confused! -- 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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