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Re: Creating a Complex System using XSLT. Step 1: Create Feedback

• To: xml-dev@l...
• Subject: Re: Creating a Complex System using XSLT. Step 1: Create Feedback
• From: "Dimitre Novatchev" <dnovatchev@y...>
• Date: Mon, 13 Oct 2003 06:44:05 +0200
• References: <3F89B9C0.4570554A@m...>
• Sender: news <news@s...>

Such type of problems are generally solved by the "iter" and "iterUntil"
templates of FXSL.

"iter" iterates a function a given number of times. "iterUntil" iterates a
function until some condition (constraint) has been met.

The solution is natural and reflects a well-formulated and well-understood
problem.

The "within" template can be used to capture "converging" behaviour. It
iterates a given function until the difference between two consecutive
results becomes less than a given range.

There are many examples, demonstrating the use of these templates in FXSL.
They have been successfully used to solve many problems of this kind.

A solution to your problem will be straightforward once the "step-function"
and the "constraining function" have been precisely defined.

I would be glad to help -- please, do not hesitate to contact me.


=====
Cheers,

Dimitre Novatchev.
http://fxsl.sourceforge.net/ -- the home of FXSL



"Roger L. Costello" <costello@m...> wrote in message
3F89B9C0.4570554A@m...">news:3F89B9C0.4570554A@m......
> Hi Folks,
>
> I would like to see if collectively we can create a complex system
> using XSLT.  Several people have been hinting at doing this.
> Now let's do it!
>
> I thought that a good first step in building a complex system would be
> to learn  how to create "feedback".  Let me start by defining feedback.
>
> Suppose that the "system" is a Fitness Center. Let's see how feedback
> may enter into a Fitness Center system:
>
>             1. New people join the Fitness Center.
> +  +>   2. This results in increased revenue.  With the new money
> +             the Fitness Center purchases more equipment.
> +         3. The new equipment attracts more people to join. +
> + + + + + + + + + + + + + + + + + + + + + + + + + +  +  +
>
> This feedback loop is "amplifying" (increasing):
>    - the number of members
>    - the total revenue of the Fitness Center
>    - the amount of equipment.
>
> This is called "positive feedback".  Positive feedback means that big
> things have a tendency to get even bigger, e.g., big Fitness Centers
> get bigger, big newspapers get bigger, etc.
>
> The amplification will reach a steady state once the Fitness Center has
> as much equipment and members as it can hold, given the size of the
> building they are in.  Thus, the size of the building imposes a
> "negative feedback" on the system, keeping it from expanding
> indefinitely.
>
> The initial stimulus which resulted in the system entering into the
> feedback loop was that some new people joined the Fitness Center.
> A small change in the system resulted in a big overall change;
> aka The Butterly Effect.
>
> Now let's relate this to XML and XSLT.  The Fitness Center is
> modelled using XML:
>
> <FitnessCenter>
>     <Members>
>         <Member level="platinum">
>             <Name>Jeff</Name>
>             <MembershipFee>$500</MembershipFee>
>         </Member>
>         <Member level="gold">
>             <Name>Stacey</Name>
>             <MembershipFee>$350</MembershipFee>
>         </Member>
>         ...
>     </Members>
>     <TotalRevenue>$75,000</TotalRevenue>
>     <Equipment>
>         <Item>Cybex Leg Extension</Item>
>         <Item>Hammer Strength Lat Row</Item>
>         ...
>     </Equipment>
> </FitnessCenter>
>
> How can we design our XSLT stylesheet to exhibit feedback?  One
> thought might be to create a stylesheet which "simulates" the growth of
> the Fitness Center:
>
> FitnessCenter.xml --> FitnessCenter.xsl -->  newFitnessCenter.xml
> Parameter: New Members List
>
> The stylesheet inputs the FitnessCenter XML document along with a
> stylesheet parameter that contains a list of new members.  The
> stylesheet then simulates the feedback loop by generating new
> <Equipment> items, which then results in creating new <Member>
> elements, which results in generating new <Equipment> items,
> which then results in creating new <Member> elements, etc.  The
> output XML document shows an updated Fitness Center with more
> members, a larger total revenue, and more equipment.
>
> However, I don't feel that such a "simulation stylesheet" would be a
> good example of feedback for this reason:
>
>    - XSLT is not really a simulation language.  If the purpose is to
>      run a simulation then it would probably be better to use a
>      language explicitly designed for simulations.
>
> So how can we write a stylesheet which exhibits feedback and takes
> advantage of what XSLT is good at - processing XML documents?
> Answer: I don't know.  I am hoping that collectively we can arrive
> at a good example.
>
> Here are some thoughts: the above example shows the feedback loop
> amplifying the member count, the total revenue, and the equipment
> count.  Perhaps that's the wrong thing to focus upon.  That is focusing
> upon the Fitness Center.  Perhaps instead the focus should be on the
> stylesheet itself.  Perhaps some aspect of the stylesheet should get
> amplified, e.g., perhaps the output of the stylesheet is another
> sylesheet which is "amplified" with more template rules.  I don't know.
> I have run into a wall.  I am hoping that someone can help me to be
> break through the wall and see the light.  /Roger
>
>
>
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• References:
  • Creating a Complex System using XSLT. Step 1: Create Feedback
    • From: "Roger L. Costello" <costello@m...>

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