I am lucky to have an adjunct teaching job at RIT teaching xml and xsl and
started to think about the questions they might ask me about why do we use
*,+,? and wondered if there was some really good answer rather than the
operators result in a closed set. I like the construct and would not imagine I
would have something better or different to offer.
Terry
----- Original Message ----
From: G. Ken Holman <gkholman(_at_)CraneSoftwrights(_dot_)com>
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Sent: Sun, February 28, 2010 2:58:58 PM
Subject: Re: [xsl] Kleene Operators
At 2010-02-28 11:48 -0800, Terry Badger wrote:
I have been using Michael Kay's XSLT book and see that the regex, XSL and DTD
occurrence operators are defined in set theory. I wonder how important this
is when we use them. I guess my question is: does something very useful
happen as the result of using these operators in XML activities that would
not have happened had we used something else?
When I teach XSLT and XQuery set theory comes into play a lot, of course mostly
when talking about the XPathy operators union, intersect and except. I find
the use of "union" is extensive, the use of "except" common and the use of
"intersect" rare in my work. In the class exercises I expect students to make
use of "union" and "except".
Kleene operators are familiar to the programmers who attend the class.
Cardinality is well known to database people.
I'm not sure where your question is coming from regarding "importance" ...
aren't all of these concepts critically important to working with information
of any kind? If we weren't using the already-familiar notation of Kleene
operators, wouldn't something else be more confusing?
This was a lesson I learned almost two decades ago when I was on the project
team developing the Near and Far graphical DTD editing tool: being a graphical
interface we implemented icons for each of the Kleene operators and found
ourselves having to teach users something new for what they already
understood. It was a drawback to use something other than what was already in
use.
I'm curious what compelled you to ask the question ... can you think of a
better way to express these concepts and you think the industry made a mistake
leveraging what is already there? I don't mean that question in a negative
sense as it may sound ... I'm really trying to understand what triggered the
question.
I hope this helps.
. . . . . . . . . . . . . Ken
--
XSLT/XQuery training: after http://XMLPrague.cz 2010-03-15/19
XSLT/XQuery training: San Carlos, California 2010-04-26/30
Principles of XSLT for XQuery Writers: San Francisco,CA 2010-05-03
XSLT/XQuery training: Ottawa, Canada 2010-05-10/14
XSLT/XQuery/UBL/Code List training: Trondheim,Norway 2010-06-02/11
Vote for your XML training: http://www.CraneSoftwrights.com/s/i/
Crane Softwrights Ltd. http://www.CraneSoftwrights.com/s/
G. Ken Holman mailto:gkholman(_at_)CraneSoftwrights(_dot_)com
Male Cancer Awareness Nov'07 http://www.CraneSoftwrights.com/s/bc
Legal business disclaimers: http://www.CraneSoftwrights.com/legal
--~------------------------------------------------------------------
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
To unsubscribe, go to: http://lists.mulberrytech.com/xsl-list/
or e-mail: <mailto:xsl-list-unsubscribe(_at_)lists(_dot_)mulberrytech(_dot_)com>
--~--
--~------------------------------------------------------------------
XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
To unsubscribe, go to: http://lists.mulberrytech.com/xsl-list/
or e-mail: <mailto:xsl-list-unsubscribe(_at_)lists(_dot_)mulberrytech(_dot_)com>
--~--