Re: Web-Prolog server demo

> Hi all,
>
> Torbjörn sent a little program to communicate with Prolog using a
> browser.  This problem has some interesting aspects that have been
> discussed here several times:
>
>    * Deal with state in Prolog web-servers, where the state is
>    maintained on the Prolog stacks (stack, choicepoints, variables).
>
>    * Deal with interactive web-applications (AJAX)
>
>    * Deal with safely calling Prolog code

> Please find below some of the discussion.  I've put the current code
> in a new GIT repository on www.swi-prolog.org.  See
>
> http://www.swi-prolog.org/git/web-prolog.git
> or git clone git://www.swi-prolog.org/home/pl/git/web-prolog.git
>
> Who is interested in helping?
>
> Cheers --- Jan
>
> On Thursday 25 June 2009 05:47:05 pm Torbjörn Lager wrote:
>> Jan,
>>
>> That looks great! I also got myself a valuable lesson, not only for
>> how deal with threads in SWI, but also how to debug, etc.  Please go
>> ahead and make that announcement on the list. I suppose an N-queens
>> demo or something would work, and if no one else steps forward, I'm
>> sure I could build one myself.
>>
>> I was also thinking about creating a small javascript library to  
>> accompany
>> the code - something that encapsulates the first-next-stop protocol.
>> But in order to avoid a dependency on any particular Javscript
>> library, maybe it's better to have the server return errors if things
>> show up in the wrong order? (I commented out the button selection  
>> code
>> and I as was the able to break the server...).
>>
>> What would be the proper way to handle (secure, perhaps also with
>> restrictions on size) uploads? To load them into a module created  
>> with
>> the name of the session?
>>
>> Shouldn't we rather put safe/1 in a module of its own? Seems somewhat
>> orthogoal to the rest of the prolog_server module...
>>
>> I think spending time on this library is well worth the effort - so
>> many interesting apps one could build on top of it!!
>>
>> BTW, did you check out my chat-demo? Simple, but still something that
>> people might want to do.
>>
>> Thanks!
>>
>> Best,
>> Torbjörn
>>
>> 2009/6/25 Jan Wielemaker <J.Wielemaker@...>:
>>> Torbjörn,
>>>
>>> I used your file as a source of inspiration. See the modified  
>>> version
>>> attached. There where some issues in your thread handling. Notably,
>>> there is little reason to spawn the server threads, but there is  
>>> reason
>>> to manage the solving threads. Also, /prolog/next *can* arrive on a
>>> different thread!
>>>
>>> Would be nice to modularise this a bit further and add support for
>>> upoading a program. If we can get all this working we might be  
>>> able to
>>> create a nice tool for the community and a nice demo for handling  
>>> state
>>> through Prolog web-servers.  One of the issues in safe compilation.
>>>
>>> Now, I just send the files to you privately. Shall we (you? I?)  
>>> make a
>>> query on the list to see if there are people willing to turn this  
>>> into
>>> a nice example and Prolog-demo?
>>>
>>>       Cheers --- Jan
>
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