Domain Modeling Made Functional

Apply Scott Wlaschin's "Domain Modeling Made Functional" (Pragmatic Bookshelf, 2018) — the functional rendering of domain-driven design. Covers making illegal states unrepresentable through algebraic data types, designing workflows as type signatures (Command → AsyncResult<Events, DomainError>), modeling errors as values via the three-track railroad (domain errors / infrastructure errors / panics), single-case wrappers for primitive obsession, choice-of-states for aggregates, DTO-to-domain translation at bounded-context edges, persistence ignorance via functional-core/imperative-shell, the impureim and Recawr (read-calculate-write) sandwich for structuring an application service as impure-pure-impure, dependency rejection and decoupling decisions from effects (the domain takes data and returns decisions/events rather than injecting dependencies), and workflow composition by chaining typed steps. Use when designing a new domain workflow / aggregate / API endpoint in a typed language (F#, Scala, Kotlin, TypeScript, C# with records + LanguageExt); when reviewing a domain model and asking whether its invariants are encoded in the type system vs in runtime guards; when refactoring exception-based domain code to errors-as-values; when explaining "make illegal states unrepresentable" or "workflows as type signatures"; when looking at a record bristling with `Option<>` and sibling-exclusive bools and wondering if it should be a sum type; when a team uses OO DDD (Evans/Vernon) but wants to lean into the type system; when structuring an application service as an impureim sandwich, or asking how to keep the domain pure when a decision needs an external call (re-quote, re-price) partway through. Strong complement to `domain-driven-design`, `hexagonal-clean-architecture`, and `clean-code` — those handle the organizational and strategic side, this skill handles the type-encoding side. Skip for dynamically-typed codebases (Python, Ruby, vanilla JS) where the techniques don't have a compiler to back them; for strategic-DDD questions about bounded contexts and ubiquitous language (use `domain-driven-design`); for pure OO pattern questions (use `solid-principles`, `responsibility-driven-design`).

mkdir -p ~/.claude/skills/domain-modeling-made-functional
curl -L https://claudskills.com/skills/domain-modeling-made-functional/SKILL.md \
  -o ~/.claude/skills/domain-modeling-made-functional/SKILL.md

@misc{domain-modeling-made-functional-2026,
  author    = {vnovakovits},
  title     = {Domain Modeling Made Functional [Claude Code skill]},
  year      = {2026},
  publisher = {ClaudSkills},
  url       = {https://claudskills.com/skills/domain-modeling-made-functional/}
}