The IF post you want to look at, though, is Emily’s GSW column from yesterday ( http://www.gamesetwatch.com/2009/05/column_homer_in_silicon_the_co_1.php ). It’s specifically about a rule-based conversation architecture, and it has the distinct advantage that it’s usable in real life. 🙂 Alabaster ( http://emshort.home.mindspring.com/Alabaster/ ) is a conversation-centered I7 game that uses this model.

http://www.eblong.com/zarf/essays/rule-based-if/index.html

For The Witch’s Yarn, I cobbled a language together to allow theatrical conversations, dialog between multiple characters per user choice. It took about three days to write the compiler in Python. Basic structure was:

BLOCK name
ADD choices of blockNames to list after dialog finishes.
REMOVE choices
IF pythonExpr THEN
ELSE
ENDIF

0 What is that dog doing here? [player is char 0. limit one 0 line per block]
1 Woof woof!
2 No way! Timmy’s trapped in the old well?
1 whimper
3 Do you really believe he is talking with that dog?

[] comment delimiters

(there were other useful keyword commands, but those were the work horses)
ENDBLOCK

ASSIGN 1 TheDog
ASSIGN 2 Bill
ASSIGN 3 Ted

This language made it very easy and natural to write conversations. That’s a big win when you’re writing thousands of lines of dialog, keeping formatting tags to a minimum.

By leveraging the compiler, you can spit out a spreadsheet for translation and a format that will merge with the translated versions. You can also add incredibly useful (game design specific) tests to a compiler.

If I may ask, what did you decide to use in the end, Jonathan?

Take a look on AIML – It provides some hints on how to:

Resolve Synonyms: Map inputs “Hello”, “Hi there”, “Howdy” etc. onto “Hi”.

Simplify Inputs: Convert “I am feeling very happy right now” to “I am happy”.

Divide and Conquer: Split “Yes my name is Jim” into “Yes” and “My name is Jim”.

http://alicebot.blogspot.com/

You don’t have to use the same markup — but use that as a model.

And, finally — by all means, use Lua or some sort of scripting language to make everything easier. 🙂

We used XML files, but it wasn’t structured as a tree. It was simply a huge database of keywords and responses, which some notion of “context”.

What made a real difference was to have some talented people writing the dialogs. And, also, some kind a feedback — since it was a web based application, it was possible to collect actual conversations and extend her vocabulary.

So, my advice would be:

1) Use xml, but don’t make it like a tree. It should be simple and flat.

2) Hire a talented writer to write the scripts. That will make a *huge* difference.

3) Allow players to type questions (at least in beta versions of the game), and collect this material to improve your database.

Just my 2 cents.

One of the best designers in this respect is Emily Short, whose game Galatea was focused entirely on one conversation with one character. Best of Three, a more recent game, features her conversational system again. The nice thing about it is, like Mass Effect’s combat system, you select topics to talk about, without knowing exactly what your character is going to say. So you as the player get to choose a conversational path to navigate, while still being rewarded by how it plays out.

The other conversational system that intrigued me in recent years was the one in Indigo Prophecy, where you had to select an option in a limited amount of time, or else your character would give a default response that may not be optimal. This overcomes one of the problems with branching conversation trees in games like The Longest Journey, where you feel that you must drain every ounce of information out of the conversation by making sure you’ve hit every conversation branch. Indigo Prophecy made that impossible, and therefore made every conversational choice important, while maintaing pacing and tension.

Anyway, Inform 7 is a very exciting design language (especially for a non-programmer like me, it’s very intuitive), but there’s no reason to use the actual language – I’m sure you could adapt Emily Short’s approach to your own uses.

conversation = {
“init” = Monologue{
“Hello. Listen to me.”,
“It’s not safe here. We should get out of here as soon as possible!”,
“Please follow me.”,
“screw you” = Execute(function(this, data)
if (data[“insultcounter”] == nil) then
data[“insultcounter”] = 1;
return Respond(“insult”);
else
return Respond(“insult2”);
end),
“who are you?” = Monologue{
“There’s no time to explain now!”,
“screw you” = Respond(“insult”)
},
“insult” = Monologue{
“There’s no need to get offensive!”
“screw you!” = Respond(“insult2”)
},
“insult2” = Monologue{
“Fine. Suit yourself!”,
done = Abort
}

It’s purely lua, parsed automatically to a usable tree when the script is loaded for the first time, and this is done through some lua magic that allows you to run the “Monologue” function with as first argument a table by calling something as Monologue{…}.

This is quite a powerful approach, as it allows for dynamic rerouting based on the environment (through the Execute function), dynamic responses, complex trees with “goto” possibilities (through Respond), and so on. It’s also easy to read and comprehend, even for people with no coding experience. It’s working great in my game, so I can definitely recommend this approach.

The other one is Bioware’s “Mass Effect”, which uses a sophisticated dialogue system, much like the one you’ve described above (there are some things you can talk about, other things you can always ask about no matter where you are in the conversation, options that are hidden but triggered by variables). A conversation typically moves in a decided direction, but often the player has the choice of an “Investigate” option, which brings up a sub-menu, through which he or she can pick from different subjects they wish to inquire about. Lastly, there are conversational options (and small, subtle beats), that don’t occur unless the player has already performed a certain task, or spoken with another person about a given subject. In addition, some conversations are greatly altered by the order in which the player completes the game’s tasks.

For example, picking a reaction to a suggestion might look something like this:

-> Good idea
Investigate Perhaps
-> No way

Choose the “Investigate” option, and you’ll see this sub-menu:

Cargo History
Crew BACK
Captain Culture

Choosing an option from the sub-menu might lead to a quick explanation, but can also lead to further dialogue options being made available in the main menu. Let’s say that the player picks “Captain”. First, he gets a response, after which the main conversation wheel re-appears, but now it looks like this:

Captain’s drinking habit Good idea
Investigate Perhaps
Shady activities No way

It’s pretty nuanced, so it might take more than one play-through to properly absorb the system’s strengths and shortcomings, but it’ll be well worth it. Some conversations are shorter and simpler than others. Some can go a dozen different ways, depending on your choices.

Another thing is that the game does not spell out the actual line of dialogue, but rather gives a sort of “emotional reaction shorthand”. The player picks an option, and then his avatar provides the actual reaction as a piece of dialogue. Every line in the game is voiced, both the player’s own and that of the NPCs. Also, players don’t actually wait until the other character has said their piece. Rather, they are provided with the option to respond just before the other character finishes.

This is essentially done to help with the “flow” of the conversation, so there aren’t as many awkward pauses in the dialogue. This all adds up to the creation of natural-sounding conversations, rather than characters reading off blocks of text or, (and this is much to my chagrin, personally, when a game does this) the feeling that a character is “talking at you”, rather than talking *with* you. Simply put, the “Mass Effect” series is the one to watch in terms of the development of conversations and dialogue in video games.

So, I definitely recommend you play these two, if you haven’t already, because there’s a lot to be learned from them, and simply because they’re great games.

Anyway, I wish you luck on your next project. Cheers.