RE: Does XProc support event-driven processing?

I dunno, I'm thinking it sounds like taking a nice well-defined processing
model and throwing in extra goodies without a compelling use-case.  Also, I
have visions of spaghetti control-flow.  Triggers are really useful in a
database environment since they allow you to get your code to run when a
system event that is out your control occurs (ie a data update).  In xproc,
you're already running *your code*, so why do you need a trigger?

-Mike

> -----Original Message-----
> From: xproc-dev-request@w3.org 
> [mailto:xproc-dev-request@w3.org] On Behalf Of Costello, Roger L.
> Sent: Sunday, June 14, 2009 5:46 PM
> To: xproc-dev@w3.org
> Subject: RE: Does XProc support event-driven processing?
> 
> 
>  
> > could you just *always* sum the quantity * cost =
> > total-cost as a step near the end of your pipeline
> 
> Let's look beyond the particular example and generalize:
> 
>    Databases have triggers; that is, the 
>    ability to associate rules with cells, 
>    e.g. on update, insert or delete of cell A, 
>    execute rule ABC.
> 
>    I think it would be powerful to have an
>    analogous capability in XProc: if any step
>    in the pipeline updates, inserts, or deletes
>    element X, execute rule XYZ.
> 
> Then, an XProc library could be used as a "rules library." 
> The rules are triggered when certain user-defined events 
> occur in the pipeline.
> 
> What do you think?
> 
> /Roger 
> 
> > -----Original Message-----
> > From: Mike Sokolov [mailto:sokolov@ifactory.com]
> > Sent: Sunday, June 14, 2009 4:49 PM
> > To: Costello, Roger L.; xproc-dev@w3.org
> > Subject: RE: Does XProc support event-driven processing?
> > 
> > Seems naive, but could you just *always* sum the quantity * cost = 
> > total-cost as a step near the end of your pipeline (after all 
> > possibility of updating merch)?
> > 
> > -Mike
> > 
> > > -----Original Message-----
> > > From: xproc-dev-request@w3.org
> > > [mailto:xproc-dev-request@w3.org] On Behalf Of Costello, Roger L.
> > > Sent: Sunday, June 14, 2009 4:32 PM
> > > To: xproc-dev@w3.org
> > > Subject: RE: Does XProc support event-driven processing?
> > > 
> > > 
> > >  
> > > > Can you elaborate on what you mean by "changes" ?
> > > 
> > > Suppose this XML document is flowing through an XProc pipeline:
> > > 
> > > <purchases date="2009-05">
> > >     <merchandise>
> > >         <name>Sony HT-IS100 BRAVIA Home Theater Micro 
> System</name>
> > >         <cost currency="USD">299.00</cost>
> > >         <quantity>1</quantity>
> > >     </merchandise>
> > >     <merchandise>
> > >         <name>ASUS Eee PC 1000HE Netbook Computer</name>
> > >         <cost currency="USD">379.00</cost>
> > >         <quantity>1</quantity>
> > >     </merchandise>
> > >     <merchandise>
> > >         <name>Sony ICD-PX720 Digital Voice Recorder</name>
> > >         <cost currency="USD">49.00</cost>
> > >         <quantity>1</quantity>
> > >     </merchandise>
> > >     <total-cost currency="USD">727.00</total-cost>
> > > </purchases>
> > > 
> > > I think it would be powerful to be able to attach this rule
> > > to the pipeline:
> > > 
> > >    If any of the steps change the value of  
> > >    a <quantity> element, fire a step 
> > >    to update <total_cost>.
> > > 
> > > Is there a way to express this?
> > > 
> > > /Roger
> > > 
> > > > -----Original Message-----
> > > > From: mozer [mailto:xmlizer@gmail.com]
> > > > Sent: Sunday, June 14, 2009 2:26 PM
> > > > To: Costello, Roger L.
> > > > Cc: xproc-dev@w3.org
> > > > Subject: Re: Does XProc support event-driven processing?
> > > > 
> > > > Can you elaborate on what you mean by "changes" ? Where ? In a
> > > > Database ? In a file ? Which one ?
> > > > 
> > > > Regards,
> > > > 
> > > > Xmlizer
> > > > 
> > > > On Sun, Jun 14, 2009 at 4:49 PM, Costello, Roger 
> > > > L.<costello@mitre.org> wrote:
> > > > >
> > > > > Hi Folks,
> > > > >
> > > > > Does XProc support event-driven processing?
> > > > >
> > > > > Here's an example to illustrate what I mean:
> > > > >
> > > > >   Hey, any time during the pipeline processing,
> > > > >   if the value of <Purchase_Quantity> changes,
> > > > >   fire a step to update <Total_Cost>.
> > > > >
> > > > > Can you think of a way to express this in XProc?
> > > > >
> > > > > /Roger
> > > > >
> > > > 
> > > 
> > 
> > 
>

Received on Sunday, 14 June 2009 21:53:41 UTC