# Glossary

One-line definitions of OCF terms, consistent with the [specification](https://opencharacterformat.org/spec/).

- **absorbedBy:** fields that drain first when a numeric input field takes an incoming decrease (temporary hit points before hit points).
- **Action:** something a character can do that needs dice or decisions, defined as a cascade of steps (roll, choice, branch, changes, action, outcome).
- **Action log:** the record of every die face and choice in an action, and who supplied it; replaying it gives the same result.
- **Active content:** content whose effects, grants and choices currently apply: owned features, inventory, picked options, granted content, applied effects and templates on active copies.
- **Aggregate:** a formula macro that counts, sums or takes the highest or lowest of something over the character's copies (`countCopies`), the ruleset's fields (`countFields`) or a list (`countList`), with a root (`copy`, `f`, `x`) bound to each element.
- **Allocate step:** an action step that spends a budget across fields (FitD's creation dots, 5E point buy) or hands out a list of values, one per field (the standard array); a checkpoint answered with amounts.
- **App:** the program using the engine; it owns the experience (dice presentation, time, choices, storage, display).
- **Applied effect:** an entry in the character's `applied` list that turns on the effects of content the character doesn't own (Bless from an ally); the app toggles it.
- **Breakdown:** the list of effects that changed a field's value, in order, returned by computeSheet ("showing the work").
- **Change:** one edit to a character, from the fixed set of change types, applied by applyChanges.
- **Change type:** one of the fixed kinds of change (set, adjust, addItem, equip, choose, …).
- **Character file:** the standard interchange file holding a character's base state and pinned pack versions.
- **Checkpoint:** a roll, choice or allocate step in an action, where the engine either continues by itself or pauses. A roll with no dice isn't one.
- **Checkpoint policy:** the app's rules for which checkpoints continue automatically and which pause.
- **Choice:** a decision declared in content or rules: options, how many to pick, and when it applies. A value choice's options may come from a formula and be filtered by `where` (`value`); a content choice with `activate: false` picks references, not active content.
- **Choice path:** the address of a choice: an optional entry, then alternating choice IDs and picked options.
- **Competing options:** several active `set` effects on one field; the engine reports them and the recommended one, and the app picks.
- **Computed value:** a value worked out for each copy of an item from the character (a FitD cohort's quality), declared by its content type, item or templates, never saved; computeSheet returns it in `copies` and the copy's actions and follow-ups read it as `self.<name>`.
- **Condition:** a formula that must evaluate to true or false (`when`, `showWhen`, `where`, prerequisites).
- **Constraint:** a game rule in the rules data, checked against the current character, whose failure is a rules issue.
- **Content item:** one piece of content (a weapon, spell, class, playbook), mechanics only, one file per item.
- **Content type:** a kind of content a game defines in data, with fields, effects, actions and per-copy state.
- **Content-type effects:** effects and grants a content type declares for every item of the type, applied before the item's own; an item can `suppress` them by ID.
- **Context root:** a name a formula can use besides field IDs (`item`, `self`, `steps`, …), bound by where the formula appears.
- **Creation start:** a way a pack offers to create a character: a rules action, maybe with parameters, and whether an automatic run is the source's random creation (`random`).
- **Credit line:** the attribution text a pack's license requires, carried in the manifest and passed on downstream.
- **Default language:** the pack's language whose translation file must be complete and ships with the mechanics.
- **Derived field:** a field computed from a formula and effects; never saved.
- **Derived offer:** a follow-up (`while`) offered exactly as long as its condition, an imbalance on the sheet, holds: a level-up the experience has earned, or a linked character to make for an empty link slot (`create`). computeSheet derives it; it is never stored or dismissed.
- **Dice function:** the swappable function the engine calls for die faces; app-supplied or the built-in random one.
- **Dice modifier:** one of the fixed set of notation modifiers (keep, drop, explode, reroll, count successes, …).
- **Display hint:** optional presentation data (groups, priority, format, unit, `showWhen`, hidden) that never affects calculations. A display group holds fields, actions or content.
- **Effect:** a change active content makes to a field, a roll or an incoming change, with an operation, value and condition.
- **Effect operation:** one of the fixed set: add, set, multiply, atLeast, atMost, grant, rollModifier.
- **Effect scope:** whether an effect applies to a character who has the content (`holder`) or one it is applied to (`applied`).
- **Engine:** an implementation of the spec's calls; the TypeScript one is the reference engine, others are ports.
- **Entry (copy):** the character's copy of a content item: base item, templates, equipped flag, quantity, state, picks.
- **Ephemeral offer:** a follow-up (`on`, `becomes`) that a batch fired, stored in the character file until it is acted on or dismissed (a `becomes` one also until its condition is false): a concentration check after damage.
- **Exclusivity group:** choices sharing a `unique` key; an option picked in one is ineligible (`already-picked`) in the others.
- **Extends:** a pack author's permanent variant of an item, inheriting everything and overriding parts.
- **Extension (character):** app-specific data in a character file under the app's own namespace, carried along untouched.
- **Field:** one value on a character, keyed by a permanent field ID.
- **Field parameter:** an action parameter of type `id` with `of: field`, read as `params.<name>.value` and `.id`.
- **Fixed set:** a list of values defined by the spec and versioned with it (operations, modifiers, codes), published as data.
- **Follow-up:** what the rules call for on a character: a derived offer (`while`) or an ephemeral one (`on`, an adjustment, with `once` the batch's matching adjustments summed; `becomes`, a condition becoming true), with an action to run, changes to apply or (a derived one) a linked character to make. computeSheet lists them in `offers`; the engine never runs or applies one.
- **Formula:** an expression in OCF's CEL-like language with dice notation; safe, finite and deterministic.
- **Handoff:** an action step (`as: participant`) run on a participant's own character by the app, which answers the paused action with that run's outcome.
- **Grant:** an effect operation that adds a member (proficiency, tag, action) to a set field; also an item's `grants` list making other content active.
- **I18n key:** the permanent key under which player-facing text is looked up in translation files.
- **Immunity:** applied content a character can't be affected by, declared by content or the rules (`immuneTo`); a matching `applied` entry is blocked and reported as the rules issue `immune`. A query can read the candidate entry as `entry`, and any activation condition the raw `character.applied` list.
- **Incoming change:** a change about to be applied to a character (damage), which effects can modify first (resistance).
- **Inline option:** an option defined inside a choice rather than as separate content.
- **Input field:** a field whose value the player supplies and the character file saves.
- **Item field:** a typed property declared by a content type and set on each item (damage, weight).
- **Limits:** bounds on a field's final value, after effects; a value outside them is the rules issue `out-of-limits`.
- **Link slot:** a named place in the rules for another character (a scoundrel's crew), saved in the character file and read by formulas as `links.<slot>`, a view.
- **Load order:** the order the app passes packs to loadRuleset; dependencies first, later packs win.
- **Monster / NPC:** a character file like any other, usually with mostly fixed values.
- **Nested choice:** a choice inside an option, pending as soon as that option is picked.
- **Overflow:** what happens when an adjust takes an input field past a bound: another field is adjusted and this one resets (FitD stress into trauma).
- **Participant:** another character taking part in an action in one of its declared roles (a target, a helper), passed to `startAction` as a view and read as `participants.<role>`.
- **Override:** a homebrew content file that changes only the properties it mentions on another pack's item.
- **Pack:** a versioned bundle of rules and/or content with a manifest, license and translations.
- **Pack release:** the single JSON document the build produces from a pack's files; the input to loadRuleset.
- **Paused action:** an action waiting at a checkpoint, returned as plain data so it can be continued later anywhere.
- **Pending choice:** a choice that applies and still needs picks. A choice step over `{ pending }` asks them one pick at a time.
- **Per-copy state:** values tracked on a character's copy of an item (charges, shots, level), declared by its type, item or templates.
- **Pick:** one selected option in a choice, stored in the character's choices tree with its own nested picks.
- **Pool dice:** dice an effect adds to a roll's dice part (`poolDice`) before keep and drop, each recording its source.
- **Prerequisite:** a condition for having content; a false one is a rules issue.
- **Priority:** a display hint ordering groups and fields; whole numbers, 0 highest.
- **Proposed change:** a change an action returns for the app to apply, to the acting character, a target or a linked character.
- **Proposed sheet:** the character with the changes an action has proposed so far `to: self` applied, which a step with `sheet: proposed` reads; built afresh in each call, never stored.
- **Query:** a link to a set of things written as a rule: a content type plus a `where` condition.
- **Result band:** a named range of roll results (6− / 7–9 / 10+), declared in a game's rules data. A band set may work out a `value` once, which its bands read (`roll.value`).
- **Roll item:** one structured piece of an itemized roll (dice or flat), with exactly one source and tags.
- **Roll modifier:** a kind of `rollModifier` effect value (advantage, disadvantage, reroll, multiplyDice, multiply, …).
- **Rules document:** a file in a pack's `rules/` folder holding fields, content types, settings and other rules data.
- **Rules issue:** an objection by the game's rules to a valid character; reported, not blocking, unless strict mode is on.
- **Ruleset:** the output of loadRuleset: all packs merged and resolved, passed to every other call.
- **Runtime error:** a change rejected because the result wouldn't be a valid character file; the character is unchanged.
- **Safety limit:** a spec-defined cap (exploding dice, nesting depth, action steps) protecting engines from untrusted packs.
- **Shape error:** input that doesn't match the spec's JSON Schema, rejected before running.
- **Situational choice:** a roll-time choice declared in game data (advantage, cover, push yourself), or a choice the receiving player makes on one incoming change (Uncanny Dodge).
- **Source:** where a value, roll item or issue came from (field, item, entry, template, effect, situational, rules, step, app).
- **Spec version:** the version of the OCF formats and behavior; packs declare the minimum they need.
- **Split (typed damage):** a proposed adjust split into one change per tag group of a roll's items, so resistances apply per damage type.
- **Stacking key:** a label on an effect grouping it with others for the stacking policy; `source` means the effect's content item.
- **Stacking policy:** how effects sharing a stacking key combine: addAll, highestOnly, lowestOnly, playerChooses.
- **Standard copy:** a copy every character holds without the file listing it (FitD gear a table tags `standard`, the ritual the Ritual ability starts with), declared by the rules or an active item as `standardCopies`; its ID is derived from its item, and the file saves it only once it differs from its defaults.
- **Strict mode:** an applyChanges option that turns rules issues into a runtime error.
- **Tag:** a dotted label on content, fields or rolls (`damage.fire`); matches itself and every tag below it.
- **Tag vocabulary:** the tags a pack declares in its rules' `tags`; every tag the pack uses must be declared there or by a dependency.
- **Template:** content applied on top of a character's copy of an item during play (+1 weapon, Flame Tongue).
- **Template field:** an item field every template may set, declared once in the rules (`templateFields`): a magic weapon's rarity, attunement and bonuses. A copy's `item` merges its templates' values over the base item's.
- **Test suite:** plain-data cases (inputs, die faces, expected outputs) every engine runs to prove conformance.
- **Upgrade script:** data shipped with a pack version that moves saved characters from the previous version's state shape.
- **View:** another character as values: its `id` and computed values for the fields the rules declare, passed in by the app; the engine never computes the other character.
- **What-changed report:** the upgrade call's comparison of a character computed under the old and new pack versions.
- **Zero-based die:** `dNz`, with faces 0 to N − 1 (`1d100z` reads 00–99).