7.11. Character Knowledge and Reasoning

| Chapter 7: Other Characters |

| 7.11. Character Knowledge and Reasoning

A character may be endowed with knowledge and even reasoning skills. Relations form quite a good way of keeping track of such problems: for instance, we can allow characters to be acquainted with one another with a relation such as

> Lucy knows Lady Cardew.

Or we might keep track of more complicated attitudes between characters, as in Murder on the Orient Express, in which some characters suspect others of the crime.

Alternatively, we might have a list of salient facts that are important in our game. We might declare these as values, and then characters could know, learn, and forget entries as appropriate:

> A fact is a kind of value. Some facts are defined by the Table of All Known Facts.

> Knowledge relates various people to various facts. The verb to know (he knows, they know, he knew, it is known) implies the knowledge relation.

> Table of All Known Facts
> fact summary
> shoe-size "Lucy wears a size 9 shoe."
> sunset-time "Sunset is at 8:22 PM this evening."

> Lucy knows shoe-size.
> Bob knows sunset-time and shoe-size.

Or again we might keep a whole database of information in a table: the characters in Questionable Revolutions know dates, countries, and a short description for each of several rebellions and popular uprisings, while in Queen of Sheba, Solomon is able to answer who, what, where, when, and why questions about a range of topics. This kind of approach is most useful when the characters need to display a deep knowledge of a particular field. The facts stored in the Table of All Known Facts, above, are comparatively sparse, because there we are designing a game in which not all data about the world is equally valuable: Lucy doesn't know the shoe size of every person in the game, because for some reason it is only her own shoe size that matters. On the other hand, the Table of All Known Facts can store different kinds of information, whereas the revolutions table has no way of storing shoe sizes or sunset times. And Murder on the Orient Express works differently again, because it is storing knowledge that concerns people and things that already exist in the world model, rather than abstract ideas. Our way of modeling character knowledge, in other words, will depend quite a lot on what kind of knowledge it is.

The possibilities of character reasoning are similarly broad, but The Problem of Edith introduces one kind: the character has a concept of how different conversation topics relate to one another, so that when she is asked about a new keyword, she picks a response that makes the question most relevant to the conversation already in progress.

We end with a longer scenario, in which we track what the character knows about the player and the conversational state: in Chronic Hinting Syndrome, the main character guides conversation in the direction he intends it to go, with the player's sometimes-reluctant participation.

See Obedient Characters for a character who needs to be taught how to perform actions before doing them

See Characters Following a Script for a programmable robot who can be given whole sequences of actions to perform

242
| Example Murder on the Orient Express A number of sleuths (the player among them) find themselves aboard the Orient Express, where a murder has taken place, and one of them is apparently the culprit. Naturally they do not agree on whom, but there is physical evidence which may change their minds... |
WI

268
| Example Questionable Revolutions An expansion on the previous idea, only this time we store information and let characters answer depending on their expertise in a given area. |
WI

> "Questionable Revolutions" Interrogative is a kind of value. The interrogatives are who, what, when, where, how, and why. Current question is an interrogative that varies. After asking someone about something: respond to the question. After answering someone that something: respond to the question. After telling someone about something: say "You're here to ask questions." Country is a kind of value. The countries are Czechoslovakia, Georgia, Sweden, Italy, Spain. Table of Information
> topic | date | place | definition
> "velvet revolution" | 1989 | Czechoslovakia | "A bloodless revolution in Czechoslovakia, in which popular protests led to the resignation of the communist president Gustav Husak, and the election of Vaclav Havel in his place."
> "rose revolution" | 2003 | Georgia | "A revolution in which President Eduard Shevardnadze was interrupted by protesters in the middle of his speech, and forced to flee."
> "spanish revolution" | 1936 | Spain | "An anarchist and socialist movement during the Spanish civil war."
> After reading a command: if the player's command includes "[interrogative]", now the current question is the interrogative understood. To respond to the question: repeat through the Table of Information: if the topic understood includes topic entry: if the current question is what or the current question is who, say definition entry appropriately; if the current question is when, say date entry appropriately; if the current question is where, say place entry appropriately; rule succeeds; say "[The noun] shrugs." Understand "ask [someone] [text]" as asking it about. Comprehension is a kind of value. The comprehensions are vague, erroneous, and correct. Table of Understanding
> character | years | geography | general comprehension
> Dr Tweedy | correct | correct | correct
> Ms Finch | erroneous | erroneous | correct
> Ms Clarion | vague | vague | erroneous
When play begins: say "Here you are in the first class cabin, but no matter how fancy the seats are, you can still get bored circling over Zurich for three hours on end. To kill time, you and the other passengers are playing a trivia game, and the final topic is your specialty: revolutions." First Class Cabin is a room. Dr Tweedy is a man in First Class. Ms Finch and Ms Clarion are women in First Class. To say (year - a number) appropriately: choose row with character of the noun in the Table of Understanding; if years entry is correct: say "'[year],' replies [the noun] promptly."; increment the quiz score of the noun; if years entry is erroneous: let guess be a random number between 1900 and 2005; say "'[guess]?' guesses [the noun], with an air of diffidence[if guess is the year]. Which is right, as it happens[end if]."; if guess is the year, increment the quiz score of the noun; if years entry is vague: let offset be a random number between -5 and 5; let year be year + offset; say "'I think [year]. About then. Close, anyway,' replies [the noun][if the offset is 0], getting it right[end if]."; if offset is 0, increment the quiz score of the noun. To say (spot - a country) appropriately: choose row with character of the noun in the Table of Understanding; if geography entry is correct: say "'[spot],' replies [the noun] promptly."; increment the quiz score of the noun; if geography entry is erroneous: let guess be a random country; say "'Er... [guess]?' says [the noun][if guess is the spot]. Which is of course correct[end if]."; if guess is the spot, increment the quiz score of the noun; if geography entry is vague, say "'Europe,' replies [the noun] with confidence." To say (explanation - some text) appropriately: choose row with character of the noun in the Table of Understanding; if general comprehension entry is correct: say "'[explanation]'[paragraph break]"; increment the quiz score of the noun; otherwise: choose a random row in the Table of Information; say "'[definition entry]'[paragraph break]"; if the definition entry is explanation: say "[A random other person who is not the noun] looks surprised that this came out right."; increment the quiz score of the noun. A person has a number called quiz score. The quiz score of Tweedy is 48. The quiz score of Finch is 2. The quiz score of Clarion is 4. Definition: a person is other if it is not the player. When play begins: now left hand status line is "T: [quiz score of Tweedy] F: [quiz score of Finch] C: [quiz score of Clarion]"; now right hand status line is "[time of day]". Test me with "dr tweedy, where was the velvet revolution located / ms finch, when was the rose revolution / ms finch, what was the rose revolution / ms clarion, when was the spanish revolution / g / g / ms finch, when was the spanish revolution". We have so far seen several ways to write conversational characters in Inform, and we will see more before the end of the manual. This naturally raises the question, which should we use? To which the answer is: it depends on the sort of game we're writing, and what we want our characters to do. The more rich and complex the system, the more likely that it will require a lot of content; if we add question types as well as keywords, for instance, we instantly multiply the number of responses we have to write by five or six. It is not worth doing this unless there is some corresponding advantage within the game.

267
| Example The Queen of Sheba Allowing the player to use question words, and using that information to modify the response given by the other character. |
WI

235
| Example The Problem of Edith A conversation in which the main character tries to build logical connections between what the player is saying now and what went immediately before. |
WI

328
| Example Chronic Hinting Syndrome Using name-printing rules to keep track of whether the player knows about objects, and also to highlight things he might want to follow up. |
WI

Previous | Contents | Next