Foundations

This part is the atoms. By the end of it you have written enough Argon to model a domain end-to-end: the substrate that lets a vocabulary package declare metatypes in the first place, then concepts, relations, rules, computations, and a type system over them.

We start with the substrate because every other chapter in this part uses metatypes — kind, role, phase, relator — that come from a vocabulary package (UFO, in our case) built on the substrate. Knowing what those declarations actually are makes the rest of Part 2 about modeling rather than memorizing keywords.

Chapter by chapter:

• 2.1 The Argon Substrate — pub metaxis, pub metatype, pub metarel, pub decorator. The four declaration forms a vocabulary package uses.
• 2.2 Concepts and Hierarchies — Person, Tenant, Landlord, Lease, ResidentialLease, CommercialLease. The hierarchy.
• 2.3 Properties and Relations — fields, multi-valued fields, binary relations, the relator pattern, refinement-typed fields.
• 2.4 Rules and Reasoning — derive, assert, the three-engine pipeline, the tier ladder.
• 2.5 Computations and Mutations — compute for pure functions, mutation for state changes, events into the bitemporal log.
• 2.6 The Type System — primitives, generics, refinement types, subtype reasoning.

By the end of Part 2 the reader has a working, queryable, validated lease model with derived state, mutations for signing and expiry, and refinement types that catch bad data at compile time — and an understanding of which keywords are language primitives and which are package declarations.