[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

Unspecified #IMPLIED attributes in Java (was: Goals: XML ...)

  • From: Toby Speight <tms@a...>
  • To: "XML developers' list" <xml-dev@i...>
  • Date: 18 Dec 1997 16:32:39 +0000

xml implied
Peter> Peter Murray-Rust <URL:mailto:peter@u...>

> In article <>,
> Peter wrote:

Peter> Is it the question of the return value of a non-existent
Peter> attribute.  IOW what does
Peter> <FOO BAR="baz" XYZZY="" BLORT="six      spaces"/>
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.

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...)


Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!

Buy Stylus Studio Now

Download The World's Best XML IDE!

Accelerate XML development with our award-winning XML IDE - Download a free trial today!

Don't miss another message! Subscribe to this list today.
First Name
Last Name
Subscribe in XML format
RSS 2.0
Atom 0.3

Stylus Studio has published XML-DEV in RSS and ATOM formats, enabling users to easily subcribe to the list from their preferred news reader application.

Stylus Studio Sponsored Links are added links designed to provide related and additional information to the visitors of this website. they were not included by the author in the initial post. To view the content without the Sponsor Links please click here.

Site Map | Privacy Policy | Terms of Use | Trademarks
Free Stylus Studio XML Training:
W3C Member
Stylus Studio® and DataDirect XQuery ™are products from DataDirect Technologies, is a registered trademark of Progress Software Corporation, in the U.S. and other countries. © 2004-2013 All Rights Reserved.