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    <p>I agree with your initial impulse in thinking that using a number of module files would be best. I imagine that one reason for using different files would be to provide different name spaces for facts and rules which would be best expressed using the same predicates. So that, for instance, <code>Description</code> would be different for <code>room(1, Description)</code> in mission 1 than in mission 2.</p> <p>One way of achieving this would be by accessing private, non-exported predicates in each of the different mission-modules. (<em>Aside</em>: I read Jan Wielemaker caution against this practice somewhere, but I'm not sure why, nor am I sure that I did read this.)</p> <p>Here's a possible pattern I threw together:</p> <p>Given a main file, 'game.pl', with the following program,</p> <pre><code>:- use_module([mission1, mission2]). start :- playing(mission1). playing(CurrentMission) :- read(Command), command(CurrentMission, Command), playing(CurrentMission). command(_, quit) :- write('Good bye.'), halt. command(CurrentMission, Command) :- ( current_predicate(CurrentMission:Command/_) % Makes sure Command is defined in the module. -&gt; CurrentMission:Command % Call Command in the current mission-module ; write('You can\'t do that.'), % In case Command isn't defined in the mission. ). </code></pre> <p>and these mission modules,</p> <p>In file 'mission1.pl':</p> <pre><code>:- module(mission1, []). turn_left :- write('You see a left-over turnip'). eat_turnip :- write('You are transported to mission2'), playing(mission2). % Return to the prompt in `game` module, but with the next module. </code></pre> <p>In file 'mission2.pl':</p> <pre><code>:- module(mission2, []). turn_left :- write('You see a left-leaning turncoat.'). </code></pre> <p>Then we can play this shitty game: </p> <pre><code>?- start. |: turn_left. You see a left-over turnip |: eat_turnip. You are transported to mission2 |: turn_left. You see a left-leaning turncoat. |: quit |: . Good bye. </code></pre> <p>The specifics of this program are problematic for a number of reasons. For instance, I expect we might rather have a single predicate that handles navigating through places, and that we'd rather describe places and object that react to different commands in our missions, rather than account for every possible command. But the general principle of using the different files would still work.</p> <p>Another approach would be to use <code>consult/1</code> and <code>unload_file/1</code> to load and unload modules, in which case you should be able to use their public, exported predicates instead of calling them by module. Documentation for those and related predicates can be found in the manual in the section <a href="http://www.swi-prolog.org/pldoc/man?section=consulting" rel="nofollow">"Loading Prolog Source Files"</a>.</p>
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    1. POOpen .pl file and close current one in SWI - Prolog
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    1. POOpen .pl file and close current one in SWI - Prolog
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    1. COwhat does `module` do?
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    2. COThe main reason I don't want to create one big file is because it would be 10000 lines of code,hence making it hard to read/edit/whatever
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    3. CO@NickShev Ah! `module/2` declares the current file to be a module! The second argument (empty lists in this case) is where you put exported predicates. If, for instance, you where you using the other approach I mention (`conulst/1` and `unload_file/1`) then you might want to export, e.g., the places in each mission: `:- module(mission1, [place/3])` (this supposes that each place is described by a 3-arity predicate, like, maybe, place(<name>,<description>,<present objects>) ). Documentation SWI modules is [here](http://www.swi-prolog.org/pldoc/man?section=modules).
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