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From thomas <tho...@stray.net>
Subject Re: Spring "web flow" vs Cocoon Flow/Continuations
Date Fri, 13 May 2005 10:30:27 GMT


--On Freitag, 13. Mai 2005 12:07 Uhr +0200 Sylvain Wallez 
<sylvain@apache.org> wrote:

> 3 years ago, the cocoon devs were discussing "flow maps", and addition to
> the sitemap to define page flow using an XML grammar. We always ended up
> with verbose XML languages having control structures (the infamous "if"),
> and then some people came with continuations, at first is Scheme (a Lisp
> dialect - eck!) and then Javascript, and later pure Java.
>
> Having a real programming language allow to *very easily* write complex
> page flows, as you can use all the language's features for control
> structures, and simply use regular variables to store the interaction
> state. Amazingly easy and powerful.
>
> The main advandage I see to a declarative approach is that it allows to
> build visual tools (i.e. graphical editors) to design the flow. But the
> underlying XML files are very likely to be a real mess in realworld
> complex use cases.
>
> Note however that Cocoon's flow engine is pluggable and that we have 3
> versions of it today:
> - flowscript, using Javascript to define the flow (business logic should
> be kept in Java)
> - javaflow, a pure java implementation
> - apples, an experimental implementation (used in Daisy IIRC) which may
> be actually closer to Spring's approach.

as i understood it the results of a flowscript-operation don't generate 
sax-events. so you can use flowscript only at the end of a pipeline. is 
that true? and is it equally true for all 3 flow-implementations mentioned 
above? in that case i would think that some logic within the sitemap (the 
infamous "if") wouldn't be so bad (for very comlex problems one could still 
decide to leave the sax-stream and use flows). but i might very well 
overlook something obvious or essential.

thanks for your time,
thomas



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