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Examining one rule in detail

An adventure is made up of rules, which define commands and replies.

Audio Adventures (or "Audioventures" for short) consist of saying
commands and listening to replies. All the possible commands and their replies are stored in a long list of rules.

Only some commands are active at once.

It would be a boring adventure if all the commands were active at the same time. This would mean there would be too many commands to choose from, and the available commands would be the same on every turn. Nothing could be accomplished by the adventurer
because accomplishments result in new things that can be done, and new replies that couldn't be heard before.

When a StoryHarp player says a command, the program matches what the player said to a command in one or more of the available rules. The matching rule or rules are used to determine what speech and sound to output in response. Matching rules may also specify changes to the state of global
variables in the adventure world. A rules command can be available or unavailable depending on the state of these global variables and how they interact with other parts of the rule.

Rules have other parts that control the interaction.

Central to writing an interesting interactive adventure is controlling what commands are active for each turn. To support this, in addition to a slot for a command and a reply, every rule has four more slots. These are:
context, move, requirements, and changes. A rule must always have a context and a command, but the other fields are optional. Usually at least one of the other four rules is filled in. Every StoryHarp adventure is simply a long list of these rules, each with only these six fields. The complexity is all in how you put rules together to build an adventure.

A context can be a location, and a move changes the current location.

It is easiest to start thinking of context as a location and a move as a way to change the current location (called the
focused context). So for example, if you had a location called 'lobby', you might make a rule with these values for the fields:

go over to the front desk
You go over to the front desk.
front desk

This translates to:

When the player is in the lobby, saying go over to the front desk will move them to the front desk, with a reply of You go over to the front desk.

This command will only be available if the 'lobby' context is active which typically means the lobby is the focused context. If you wanted a command to 'go back to the lobby' from the front desk, you would set up a command with 'front desk' as the context , 'lobby' as the move, and 'go back to the lobby' as the command, like so:

front desk
go back to the lobby
You go back to the lobby.

Here is an example of a complete rule.

Now we will examine a single rule in detail, looking at all the fields in the rule.

This is the most important variable that must be true for the command to be available.

by the fireplace in the hotel lobby
This is a phrase the adventurer may speak. All currently available commands are told to the player when they say 'options'. If the phrase is prefaced by a '$', as in '$swordfish', the player must guess the phrase, and it will be described as 'an answer to a riddle' when options are requested.

examine the vase

This is something to be told to the player by the computer (via text-to-speech software). The reply may include sounds, inserted as
{sound XXXX}, and music, inserted as
{music YYYY}.
You find a slip of paper underneath the vase and put it in your pocket. {sound paper rustle} Just then the hotel manager comes along, grabs you, and roughly shoves you out the front door, saying "Really, enough poking around already. You're disturbing the guests. Don't come back." {sound door slam} In the scuffle, your glasses get stepped on and are crushed. {sound crushed glass}

The move is a context that will be set as the focused context after the user says the command in this rule. This simulates moving from one location to another.
(The more general explanation is: A move is a new primary variable to be set to true. The previous primary variable is set to false. The primary variable is called the focus, and usually is used as a context.)

outside the hotel
This is list of variables (besides the context) that must be true or false for the command to be available. A leading '~' means the variable must be false; otherwise it must be true. All the listed variables must be in the correct state for the command to be available.

wearing glasses
This is a list of other changes that make variables true or false. A leading '~' means the variable will be set to false when the command in this rule is said; otherwise the variable will be set to true (if not already true).
holding the slip of paper
barred from the hotel
~wearing glasses
Here is how the example rule will play out.

If you meet the requirements of standing by the fireplace in the hotel lobby, and are wearing glasses and are not dizzy, you can say the command "examine the vase". If you do so, then you get a long reply with sound effects, a focus move to outside the hotel, and changes made so you are now holding the slip of paper, barred from the hotel, and not wearing glasses anymore. Each underlined item has an associated global
variable of the same name.

Before you do this command, the focus will probably be by the fireplace in the hotel lobby. After the command, the focus will be outside the hotel. The crushing of the glasses is represented by setting wearing glasses to false. Having found the slip of paper is represented by setting holding the slip of paper to true.

See also:

Essential definitions

A simple example audioventure

Top twelve tips for authoring audioventures

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Updated: March 10, 1999. Questions/comments on site to
Copyright © 1998, 1999 Paul D. Fernhout & Cynthia F. Kurtz.