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From Stefano Mazzocchi <stef...@apache.org>
Subject Re: [Schecoon] flow control layer
Date Fri, 01 Mar 2002 14:16:09 GMT
"Piroumian, Konstantin" wrote:
> 
> Good day!
> 
> <skip>
> > > > > Built-in datatypes are numbers, arrays, dictionaries and function
> > > > > objects. There is a special type 'void', that has a single possible
> > > > > value named 'void'.
> > > >
> > > > What about 'strings', 'dates' and the like?
> > >
> > > Oh, yes, those too ;-) I forgot about them.
> >
> > ok, I would add 'currency', since web-oriented flow languages will sure
> > have to deal with strings, dates and money. And having them explicitly
> > declared in the language might allow us to obtain 'easy' transparent
> > handling (say, automatic money conversion)
> 
> Hm... Money conversion can be a complex business operation depending on
> external environment.

Ok, you're right, this should probably be left to some deeper business
logic deployed someplace (like in an EJB, WebService or external class).

> >
> > Are there any other 'first class concepts' that you guys might want to
> > have in a flow language? IDs (as for credit-card numbers) might be
> > another one, even if probably a concept too detailed... ok, your turn
> > people :)
> 
> What about EJB objects?
> A DOM object would be also useful.

Well, these things are already available as you can connect with java
very easily (at least, this is what I want: flowmaps will be 'glue'
between your business logic, nothing really fancy  there).

So, probably, even Dates should be left out and delegated to the java
classes (which are good already, so less things to write for us and less
bugs to find!)
 
> Speaking frankly, I've already seen something like this we are discussing in
> WebLogic Process Integrator (it's a Workflow Engine). 

Well, yes, a workflow is a special kind of 'flow', by definition, I
would say :)

> You can define your
> workflow process using a GUI (it looks like a flow chart diagram) and among
> the other types you could define workflow variables of the following types:
> Object, EJBObject, XML.

Yes, GUI driven authoring of flows is probably possible, just like it
could be possible to provide a sort of GUI authoring process for
sitemaps, but this is a separate concern.
 
> Also, this is related more to other thread about XML-based selectors: in
> WLPI you could define your selection logic using built-in functions and you
> could combine XML-based selection with other types, e.g.:
> 
> <if test="XPath($userInput, '/confirmation/response')='yes' and
> compareDate($startDate, $endDate)=0'" >...</if>
> where $userInput is type of 'XML' (internally it could be a DOM object) and
> $startDate, $endDate are of 'java.util.Date'.

I still believe that using the XML syntax to program flows is using the
'hammer' antipattern: 'when you have a hammer, everything looks like a
nail'.

Think about it.

-- 
Stefano Mazzocchi      One must still have chaos in oneself to be
                          able to give birth to a dancing star.
<stefano@apache.org>                             Friedrich Nietzsche
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