When is an attribute an attribute?
cbullard at hiwaay.net
Tue Apr 7 02:38:36 BST 1998
Roy Tennant wrote:
> I've been trying to figure this out for a while with no success. It seems
> to me that there are several quite different ways one can encode
> information in XML. Are all of the following correct?
> When and why would
> you choose one over another? Does it matter? Thank you for your indulgence
> as I puzzle out what must surely be readily apparent to most of you.
Ok, a DTD really helps this sort of discussion along, but
> Example 1:
> <BOOK TITLE="The Call of the Wild" AUTHOR="London, Jack"\>
Use empty elements and attributes for tag bags, basically,
if the datum has no frequency and order requirements (only
occurs once somewhere in the attribute list).
NOTE: I haven't looked to see if XML dropped the
SGML restriction on repeated values in attlist
> Example 2:
> <BOOK AUTHOR="London, Jack">The Call of the Wild</BOOK>
Use this if you don't care that the string inside the
tags is only differentiated by the BOOK, that is,
semantically, there is no difference between this
<BOOK AUTHOR="London, Jack">Love that Wolf!!</BOOK>
or IOW, your application has to know that is a title.
> Example 3:
> <TITLE>The Call of the Wild</TITLE>
> <AUTHOR>London, Jack</AUTHOR>
Use this when it is important to know there
is a title and author (i.e, this BOOK
HAS-A TITLE, HAS-A AUTHOR; the
string, The CALL of the WILD IS-A TITLE).
Given the element type declaration, you can tell which order
they should come in, are there multiple
authors, are there alternate titles, etc.
The semantic is application dependent. For
a linking semantic, you might be counting
nodes inside the BOOK. For rendering,
you might be assigning the font value
based on the context of the book element.
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