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Mora

Declarative datalog for Skyrim Special Edition.

Mora is a small language for describing how Skyrim's data should look and how it should react at runtime. You write rules; Mora evaluates everything it can at compile time against your real ESP/ESM load order and bakes the results into a flat, memory-mappable patch file. An accompanying SKSE plugin mmaps that file, applies the static patches on game load, and runs a small differential-dataflow engine for the rules that have to wait for live game state.

2.5M patches applied in under 10ms, zero runtime rule evaluation.

Quick Example

namespace my_mod.balance

use form :as f

# All iron weapons get 20 damage — fully static, baked into the patch file.
iron_weapons(W):
    f/weapon(W)
    f/keyword(W, @WeapMaterialIron)
    => set form/damage(W, 20)

$ mora compile balance.mora --data-dir "~/.steam/.../Skyrim Special Edition/Data"
  Mora v0.1.0
  [OK] Parsing 1 files
  [OK] Resolving 1 rules
  [OK] Type checking 1 rules
  [OK] 1 static, 0 dynamic
  [OK] 200 patches -> mora_patches.bin

With auto-detection, mora compile places mora_patches.bin in Data/SKSE/Plugins/ for you. Drop MoraRuntime.dll next to it and launch the game. That's it.

Why Mora?

  • Static-first. Anything derivable from ESP data is fully evaluated at compile time. The patch file is literally a sorted table of (FormID, field, op, value) tuples; applying a patch is one memory write.
  • Dynamic when it has to be. maintain rules track truth values over live game state and auto-retract effects when conditions stop holding. on rules fire edge-triggered on events.
  • Unified vocabulary. Five built-in namespaces — form/, ref/, player/, world/, event/ — cover record data, live references, player state, global state, and events, with explicit bridges between them.
  • Metaprogrammed. A single constexpr relation table drives the parser, type checker, runtime dispatch, and these docs. New relations are an additive one-line change.

Get Started

  • Getting Started — install, write your first rule, compile it, run it in-game.
  • How Mora Works — the three-tier rule model, the .mora.patch binary format, the runtime engine.
  • Language Guide — a walk-through tutorial covering syntax, types, verbs, maintain/on, arithmetic, and examples.
  • Language Reference — types, verbs, operators, built-in functions.
  • Relation Reference — the full inventory of built-in relations, auto-generated from data/relations/**/*.yaml.
  • CLI Reference — every mora subcommand and flag.
  • Examples — annotated .mora files, including the bandit bounty rule.