[MUD-Dev] TECH: Question about Bartle's new book

[Richard A. Bartle]

On 02 September 2003, Christer Enfors wrote:
> On page 291, footnote 51, Bartle writes:

>    "I put a smimple expert system into MUD2 to control mobiles in
>    fights, but toned it down because it turned out to to be better
>    than many players. It's merely a question of balance."

> This sounds very interesting. Does anybody know where I can get
> more information about this expert system, and a rough overview of
> how it was originally designed? And in what way he toned it down?

OK, well there are some standard strategies meaningful for MUD2,
which I coded in directly. These are of the "if I am carrying a
heavy object I don't need, drop it" variety, and they were the
default behaviour. However, some of these detected conditions where
it could invoke a proper planning system. The planning system
operates on a list of actions that are to be executed in sequence
whenever it's time for the mobile to act. The actions in the
planning system override the default behaviour, and can include
planning and sensing actions (ie. a plan could be something like,
"remove my opponent's magical protections, then if they're not blind
cast a blindness spell on them, otherwise think of some other spell
to cast on them"). These actions were themselves hard-coded, though
- the planner wasn't sophisticated enough to be able to introspect
on them.

The system worked by taking the first action in the plan and
executing its code. This may or may not involve some "physical"
actions, and may or may not involve alteration to the plan. When the
plan was empty, it defaulted to the standard hard-coded (and if you
knew your stuff, predictable) basic reactive system.

As for toning it down, I did this in two ways: by putting guards on
some actions such that they wouldn't be inserted in the plan for
more stupid mobiles (zombies aren't as smart as goblins); by adding
in some randomisation, so that mobiles would sometimes not put the
best action in the plan or would not do the best response in the
hard-coded part.

As I said in the footnote, it was only a simple expert system
(mainly because of the overheads in CPU use if I'd gone for
something beefier). However, when inexpert players were faced with
it they tended not to know the best thing to do in the situation
themselves and consequently lost when perhaps they shouldn't
have. That's why I toned it down.

I do use the planning system for other activities (mobiles giving
one another orders to try to counter attacks by multiple players,
that kind of thing) but I never really pushed it hard; it was more
of a luxury borne from my interest in AI, rather than anything the
gameplay actually needed.

		Richard
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