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List:       kde-devel
Subject:    Re: RFC: Parallel execution paths in WorKflow
From:       Thomas Kadauke <tkadauke () gmx ! de>
Date:       2006-06-29 12:42:37
Message-ID: 200606291442.37710.tkadauke () gmx ! de
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Hi John,

Am Thursday 29 June 2006 03:28 schrieb John Tapsell:
>   More important (for me) than branching, is parallelism.
>
>   When you have "get files" does it get all the files first, then
> proceed to the next step, or does it start modifying the images as it
> gets each file, thus it can be getting some files while modifying the
> ones it already has so far.

While I can see that this is incredibly useful, I don't think that I'll be 
able to do that. The main reason for this is that workflows can be 
interactive, which means that the user is asked for missing fields in 
commands while the workflow is run. Also, suppose that you made pictures with 
you camera, and some of them are portrait, some of them are landscape. Then 
you don't want to rotate all pictures the same way. In this case, interactive 
processing *per picture* is neccessary. With parallelism of commands the user 
would be confused, if multiple commands in a workflow are interactive, since 
the "questions" asked at runtime would seem to have a random order.

>   Also I'd really like to be able to watch a directory.

That's a cool thing. I'd implement this (and the workflows you described) with 
a konqueror plugin which integrates WorKflow into konqueror (file browsing 
mode). The konqueror plugin would trigger the execution of a workflow, in 
this case when a file is added in the current directory.

Another possibility would be to have workflows run in "daemon mode". Then, 
you'd have a "Watch Directory" command, which would trigger the workflow's 
execution when a file is changed in the specified directory.

>   Here's some use cases that I have a personal need for:
>
> 1) Watch a particular smb folder for .ps file.  Download the .ps file,
> convert it to .pdf, then upload with the new pdf to the smb folder,
> keeping the filename the same except .pdf instead of .ps.

Watching smb folders is hard, AFAICS. The only way to do this would be 
polling, and polling is evil. I have to look into this further.

Downloading and uploading will be transparent to the user because of KIO. Then 
the WorKflow would consist of the commands "Watch Folder" and "Convert to 
PDF".

> 2) Watch a folder for .png files (which I generate in blender).  Do
> fancy cropping of the files.  Save the changed files in a different
> folder.

Do you mean interactive cropping here? I.e. a dialog with the image is shown, 
where you select the image's region to keep?

Thanks a lot for you input!
--Thomas
 
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