Re: [xml-dev] XRules: Mind your own business rules

[David Lyon <david.lyon@computergrid.net>]

Hi Waleed,

Excellent idea... I really *really* like it.....

On Thu, 10 Mar 2005 5:16 am, Waleed Abdulla wrote:
>
> <xr:ruleset context="/PurchaseOrder/Item">
>   <xr:calculate target="ItemTotal" value="UnitPrice * Quantity" />
>   <xr:bind target=".">
>     <xr:property name="OverLimit" dvalue="boolean(. &gt; ../MaxPerItem)" />
>   </xr:bind>
> </xr:ruleset>
>
> And, this is a sample purchase order:
>
> <PurchaseOrder>
>   <MaxPerItem>300</MaxPerItem>
>   <Item>
>     <Quantity>2</Quantity>
>     <UnitPrice>30</UnitPrice>
>     <ItemTotal>60</ItemTotal>
>   </Item>
> </PurchaseOrder>

Maybe I could use it in my markup?

I would embed the calculations directly in the xml.. Here I've
added an explanation mark to denote a formula, and keeping
the # to denote that the field return type will be a number or 
a ? in the case of a boolean. This would give me something 
a little more compact that would look like this:

 <PurchaseOrder>
   MaxPerItem#=300
   <Item>
     Quantity#=2
     UnitPrice#=30
     ItemTotal#!="UnitPrice# * Quantity#" 
     OverLimit?!="Quantity# > ../MaxPerItem"
   </Item>
 </PurchaseOrder>

There are a number of applications in real life business
documents for this:

 - US sales tax calculations
 - Intercountry tax/GST/VAT issues
 - (the afformentioned) shipping costs
 - the ability to incorporate events.. 

Actually this whole idea is not dissimilar to linking
and calculations within spreadsheets. Providing the
scope stays within the document... I think that it is
quite a good idea.

It's definitely something worth pursuing further !

Best Regards

David

-- 
Computergrid : The ones with the most connections win.