Core Concepts

A Modality contract is three artifacts:

contract/
├── state/     # posted data (identities, evidence)
├── model/     # possible moves (labeled transition system)
└── rules/     # who / when / under what predicates

A commit is accepted only if it is signed as required, is a valid model transition, and satisfies every accumulated rule. No valid witness means the commit is rejected.

The rest of this guide names the pieces that make that check possible.

The Five Pillars

Concept	Purpose
Append-only log	Immutable, ordered history
State machines	Finite, verifiable behaviors
Modal logic	Express temporal constraints
Predicates	Bind identity to logic
Potentialism	Safe accumulation of rules

How They Fit Together

1. A contract is an append-only log of signed commits
2. Commits can add state, rules, or perform actions
3. A model (labeled transition system) defines what actions are possible
4. Rules (temporal formulas) constrain which evolutions are valid
5. Predicates bind real-world identity (signatures) to logical constraints
6. Potentialism ensures rules can only shrink the space of valid futures

Dive into each concept:

• Append-Only Logs
• State Machines
• Modal Logic
• Predicates
• Potentialism