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Functional and Algebraic Domain
Modeling
Debasish Ghosh
@debasishg
関数型、代数的なドメイン・モデリングの方法
Saturday, 30 January 16
Domain Modeling
ドメイン・モデリング
Saturday, 30 January 16
Domain Modeling(Functional)
関数型なドメイン・モデリング
Saturday, 30 January 16
What is a domain model ?
A domain model in problem solving and software engineering is a
conceptual model of all the topic...
The Functional Lens ..
“domain API evolution through algebraic
composition”
関数型レンズ
代数的合成を通じたドメイン API の進化
Saturday, 30 Janu...
「サーバを関数として考える」
Saturday, 30 January 16
Twitter 社でのサーバソフトウェアの構成は fp と同じ理念
(不変性、関数の合成、副作用の分離)に基づく
Saturday, 30 January 16
Your domain model is a
function
ドメインモデルは関数である
Saturday, 30 January 16
Your domain model is a
function
ドメインモデルは関数(...であって欲しい)
Saturday, 30 January 16
Your domain model is a
collection of functions
ドメインモデルは関数の集合である
Saturday, 30 January 16
Your domain model is a
collection of functions
some simpler models are ..
具体例で考えると...
Saturday, 30 January 16
https://msdn.microsoft.com/en-us/library/jj591560.aspx
カンファレンス管理システム
Saturday, 30 January 16
A Bounded Context
• has a consistent vocabulary
• a set of domain behaviors modeled as
functions on domain objects
impleme...
Domain Model = ∪(i) Bounded Context(i)
Saturday, 30 January 16
Domain Model = ∪(i) Bounded Context(i)
Bounded Context = { f(x) | p(x) ∈ Domain Rules }
Saturday, 30 January 16
Domain Model = ∪(i) Bounded Context(i)
Bounded Context = { f(x) | p(x) ∈ Domain Rules }
• domain function
• on an object o...
• Functions / Morphisms
• Types / Sets
• Composition
• Rules / Laws
関数と射、型と集合、合成、ルールと法則
Saturday, 30 January 16
• Functions / Morphisms
• Types / Sets
• Composition
• Rules / Laws
algebra
要は代数ということ
Saturday, 30 January 16
Domain Model Algebra
ドメインモデルの代数
Saturday, 30 January 16
Domain Model Algebra
(algebra of types, functions & laws)
型と関数と法則の代数
Saturday, 30 January 16
Domain Model Algebra
(algebra of types, functions & laws)
explicit
• types
• type constraints
• expression in terms of oth...
Domain Model Algebra
(algebra of types, functions & laws)
explicit verifiable
• types
• type constraints
• expr in terms of...
Problem Domain
問題ドメインの例として証券取引口座を考察する
Saturday, 30 January 16
Bank
Account
Trade
Customer
...
...
...
Problem Domain
...
entities
エンティティとなるのは、口座、顧客、取引、銀行
Saturday, 30 January 16
Bank
Account
Trade
Customer
...
...
...
do trade
process
execution
place
order
Problem Domain
...
entities
behaviors
振る舞いと...
Bank
Account
Trade
Customer
...
...
...
do trade
process
execution
place
order
Problem Domain
...
market
regulations
tax l...
do trade
process
execution
place
order
Solution Domain
...
behaviors
Functions
(Type => Type)
ソリューションドメインでは、振る舞いは関数 (型 型)
...
Bank
Account
Trade
Customer
...
...
...
do trade
process
execution
place
order
Solution Domain
...
entities
behaviors
func...
Bank
Account
Trade
Customer
...
...
...
do trade
process
execution
place
order
Solution Domain
...
market
regulations
tax ...
Bank
Account
Trade
Customer
...
...
...
do trade
process
execution
place
order
Solution Domain
...
market
regulations
tax ...
Bank
Account
Trade
Customer
...
...
...
do trade
process
execution
place
order
Solution Domain
...
market
regulations
tax ...
Domain Model = ∪(i) Bounded Context(i)
Bounded Context = { f(x) | p(x) ∈ Domain Rules }
• domain function
• on an object o...
Client places order
- flexible format
1
クライアントが注文を出す
フォーマットは様々
Saturday, 30 January 16
Client places order
- flexible format
Transform to internal domain
model entity and place for execution
1 2
内部でのドメインモデルエンティ...
Client places order
- flexible format
Transform to internal domain
model entity and place for execution
Trade & Allocate to...
def clientOrders: ClientOrderSheet => List[Order]
def execute: Market => Account => Order => List[Execution]
def allocate:...
def clientOrders: ClientOrderSheet => List[Order]
def execute[Account <: BrokerAccount]: Market => Account
=> Order => Lis...
def clientOrders: ClientOrderSheet => List[Order]
def execute: Market => Account => Order => List[Execution]
def allocate:...
def clientOrders: ClientOrderSheet => List[Order]
def execute: Market => Account => Order => List[Execution]
def allocate:...
def clientOrders: ClientOrderSheet => List[Order]
def execute: Market => Account => Order => List[Execution]
def allocate:...
trait Trading[Account, Trade, ClientOrderSheet, Order,
Execution, Market] {
def clientOrders: ClientOrderSheet => List[Ord...
Algebraic Design
• The algebra is the binding contract of the
API
• Implementation is NOT part of the algebra
• An algebra...
def clientOrders: ClientOrderSheet => List[Order]
def execute: Market => Account => Order => List[Execution]
def allocate:...
def clientOrders: ClientOrderSheet => List[Order]
def execute(m: Market, broker: Account): Order => List[Execution]
def al...
def clientOrders: ClientOrderSheet => List[Order]
def execute(m: Market, broker: Account): Order => List[Execution]
def al...
def clientOrders: ClientOrderSheet => List[Order]
def execute(m: Market, broker: Account): Order => List[Execution]
def al...
def clientOrders: ClientOrderSheet => List[Order]
def execute(m: Market, broker: Account): Order => List[Execution]
def al...
def clientOrders: ClientOrderSheet => List[Order]
def execute(m: Market, broker: Account): Order => List[Execution]
def al...
def f: A => List[B]
def g: B => List[C]
def h: C => List[D]
.. a problem of composition ..
これは ... 合成の問題だ
Saturday, 30 Jan...
.. a problem of
composition with effects ..
def f: A => List[B]
def g: B => List[C]
def h: C => List[D]
これは ... 作用付きの合成の問題...
def f[M: Monad]: A => M[B]
def g[M: Monad]: B => M[C]
def h[M: Monad]: C => M[D]
.. a problem of composition with
effects ...
case class Kleisli[M[_], A, B](run: A => M[B]) {
def andThen[C](f: B => M[C])
(implicit M: Monad[M]): Kleisli[M, A, C] =
K...
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
def execute(m: Market, b: Account): Kleisli[List, Order, Executio...
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
def execute(m: Market, b: Account): Kleisli[List, Order, Executio...
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
def execute(m: Market, b: Account): Kleisli[List, Order, Executio...
def tradeGeneration(
market: Market,
broker: Account,
clientAccounts: List[Account]) = {
clientOrders andThen
execute(mark...
def tradeGeneration(
market: Market,
broker: Account,
clientAccounts: List[Account]) = {
clientOrders andThen
execute(mark...
algebraic & functional
• Just Pure Functions. Lower cognitive load -
don’t have to think of the classes & data
members whe...
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
def execute(m: Market, b: Account): Kleisli[List, Order, Executio...
more algebra,
more types
代数と型、大盛りで追加!
Saturday, 30 January 16
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
return type constructor
List は戻り値の型コンストラクタ
Saturday, 30 January 16
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
return type constructor
What happens in case the operation fails ...
Error handling as an
Effect
• pure and functional
• with an explicit and published algebra
• stackable with existing effec...
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
.. stacking of effects ..
M[List[_]]
作用の積み上げ
Saturday, 30 January...
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
.. stacking of effects ..
M[List[_]]: M is a Monad
List をエラー処理のため...
type Response[A] = String / Option[A]
val count: Response[Int] = some(10).right
for {
maybeCount <- count
} yield {
for {
...
type Response[A] = String / Option[A]
val count: Response[Int] = some(10).right
for {
maybeCount <- count
} yield {
for {
...
type Response[A] = String / Option[A]
val count: Response[Int] = some(10).right
for {
maybeCount <- count
} yield {
for {
...
Monad Transformers
• collapses the stack and gives us a single
monad to deal with
• order of stacking is important though
...
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
.. stacking of effects ..
case class ListT[M[_], A] (run: M[List[...
これは代数にとって小さな一歩だが、
ドメインモデルにとっては巨大な跳躍である
Saturday, 30 January 16
type StringOr[A] = String / A
type Valid[A] = ListT[StringOr, A]
これは代数にとって小さな一歩だが、
ドメインモデルにとっては巨大な跳躍である
Saturday, 30 Janua...
type StringOr[A] = String / A
type Valid[A] = ListT[StringOr, A]
def clientOrders: Kleisli[Valid, ClientOrderSheet, Order]...
type StringOr[A] = String / A
type Valid[A] = ListT[StringOr, A]
def clientOrders: Kleisli[Valid, ClientOrderSheet, Order]...
def execute(market: Market, brokerAccount: Account) =
kleisli[List, Order, Execution] { order =>
order.items.map { item =>...
private def makeExecution(brokerAccount: Account,
item: LineItem, market: Market): String / Execution = //..
def execute(m...
List
(aggregates)
Algebra of types
型の代数
集約のための List
Saturday, 30 January 16
List
(aggregates)
Disjunction
(error accumulation)
Algebra of types
エラー蓄積のためのDisjunction
Saturday, 30 January 16
List
(aggregates)
Disjunction
(error accumulation)
Kleisli
(dependency injection)
Algebra of types
依存性注入のための Kleisli
Satur...
List
(aggregates)
Disjunction
(error accumulation)
Kleisli
(dependency injection)
Future
(reactive non-blocking computatio...
List
(aggregates)
Disjunction
(error accumulation)
Kleisli
(dependency injection)
Future
(reactive non-blocking computatio...
List
(aggregates)
Disjunction
(error accumulation)
Kleisli
(dependency injection)
Future
(reactive non-blocking computatio...
List
(aggregates)
Disjunction
(error accumulation)
Kleisli
(dependency injection)
Future
(reactive non-blocking computatio...
List
(aggregates)
Disjunction
(error accumulation)
Kleisli
(dependency injection)
Future
(reactive non-blocking computatio...
List
(aggregates)
Disjunction
(error accumulation)
Kleisli
(dependency injection)
Future
(reactive non-blocking computatio...
List
(aggregates)
Disjunction
(error accumulation)
Kleisli
(dependency injection)
Future
(reactive non-blocking computatio...
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
def execute(m: Market, b: Account): Kleisli[List, Order, Executio...
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
def execute(m: Market, b: Account): Kleisli[List, Order, Executio...
.. the algebra ..
def clientOrders: Kleisli[List, ClientOrderSheet, Order]
def execute(m: Market, b: Account): Kleisli[Lis...
.. the algebra ..
composition
def tradeGeneration(market: Market, broker: Account,
clientAccounts: List[Account]) = {
clie...
.. the algebra ..
trait OrderLaw {
def sizeLaw: Seq[ClientOrder] => Seq[Order] => Boolean =
{ cos => orders =>
cos.size ==...
Domain Rules as
Algebraic Properties
• part of the abstraction
• equally important as the actual
abstraction
• verifiable a...
.. domain rules verification ..
property("Check Client Order laws") =
forAll((cos: Set[ClientOrder]) => {
val orders = for ...
https://www.manning.com/books/functional-and-reactive-
domain-modeling
本書いてます
Saturday, 30 January 16
ThankYou!
Saturday, 30 January 16
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Functional and Algebraic Domain Modeling

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Evolving domain models compositionally using the algebra of domain behaviors. Demonstrates the power of functional programming.

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Functional and Algebraic Domain Modeling

  1. 1. Functional and Algebraic Domain Modeling Debasish Ghosh @debasishg 関数型、代数的なドメイン・モデリングの方法 Saturday, 30 January 16
  2. 2. Domain Modeling ドメイン・モデリング Saturday, 30 January 16
  3. 3. Domain Modeling(Functional) 関数型なドメイン・モデリング Saturday, 30 January 16
  4. 4. What is a domain model ? A domain model in problem solving and software engineering is a conceptual model of all the topics related to a specific problem. It describes the various entities, their attributes, roles, and relationships, plus the constraints that govern the problem domain. It does not describe the solutions to the problem. Wikipedia (http://en.wikipedia.org/wiki/Domain_model) 特定の問題領域に関する概念モデル エンティティ/関連/制約などを記述 Saturday, 30 January 16
  5. 5. The Functional Lens .. “domain API evolution through algebraic composition” 関数型レンズ 代数的合成を通じたドメイン API の進化 Saturday, 30 January 16
  6. 6. 「サーバを関数として考える」 Saturday, 30 January 16
  7. 7. Twitter 社でのサーバソフトウェアの構成は fp と同じ理念 (不変性、関数の合成、副作用の分離)に基づく Saturday, 30 January 16
  8. 8. Your domain model is a function ドメインモデルは関数である Saturday, 30 January 16
  9. 9. Your domain model is a function ドメインモデルは関数(...であって欲しい) Saturday, 30 January 16
  10. 10. Your domain model is a collection of functions ドメインモデルは関数の集合である Saturday, 30 January 16
  11. 11. Your domain model is a collection of functions some simpler models are .. 具体例で考えると... Saturday, 30 January 16
  12. 12. https://msdn.microsoft.com/en-us/library/jj591560.aspx カンファレンス管理システム Saturday, 30 January 16
  13. 13. A Bounded Context • has a consistent vocabulary • a set of domain behaviors modeled as functions on domain objects implemented as types • related behaviors grouped as modules 境界づけられたコンテキストは、統一された語彙を持つ ドメインの振る舞いは関数、オブジェクトは型として実装するSaturday, 30 January 16
  14. 14. Domain Model = ∪(i) Bounded Context(i) Saturday, 30 January 16
  15. 15. Domain Model = ∪(i) Bounded Context(i) Bounded Context = { f(x) | p(x) ∈ Domain Rules } Saturday, 30 January 16
  16. 16. Domain Model = ∪(i) Bounded Context(i) Bounded Context = { f(x) | p(x) ∈ Domain Rules } • domain function • on an object of type x • composes with other functions • closed under composition • business rules f はドメイン関数で、他の関数と合成できる p はビジネスルール Saturday, 30 January 16
  17. 17. • Functions / Morphisms • Types / Sets • Composition • Rules / Laws 関数と射、型と集合、合成、ルールと法則 Saturday, 30 January 16
  18. 18. • Functions / Morphisms • Types / Sets • Composition • Rules / Laws algebra 要は代数ということ Saturday, 30 January 16
  19. 19. Domain Model Algebra ドメインモデルの代数 Saturday, 30 January 16
  20. 20. Domain Model Algebra (algebra of types, functions & laws) 型と関数と法則の代数 Saturday, 30 January 16
  21. 21. Domain Model Algebra (algebra of types, functions & laws) explicit • types • type constraints • expression in terms of other generic algebra これを明示的にすると、型、型の制約、他の代数を用いた表現 Saturday, 30 January 16
  22. 22. Domain Model Algebra (algebra of types, functions & laws) explicit verifiable • types • type constraints • expr in terms of other generic algebra • type constraints • more constraints if you have DT • algebraic property based testing 確認可能なのは型制約、代数的プロパティーベースのテスト 依存型があればより強い制約を検証できる Saturday, 30 January 16
  23. 23. Problem Domain 問題ドメインの例として証券取引口座を考察する Saturday, 30 January 16
  24. 24. Bank Account Trade Customer ... ... ... Problem Domain ... entities エンティティとなるのは、口座、顧客、取引、銀行 Saturday, 30 January 16
  25. 25. Bank Account Trade Customer ... ... ... do trade process execution place order Problem Domain ... entities behaviors 振る舞いとなるのは、注文、取引、執行処理 Saturday, 30 January 16
  26. 26. Bank Account Trade Customer ... ... ... do trade process execution place order Problem Domain ... market regulations tax laws brokerage commission rates ... entities behaviors laws 法則となるのは株式市場規則、税法、手数料 Saturday, 30 January 16
  27. 27. do trade process execution place order Solution Domain ... behaviors Functions (Type => Type) ソリューションドメインでは、振る舞いは関数 (型 型) Saturday, 30 January 16
  28. 28. Bank Account Trade Customer ... ... ... do trade process execution place order Solution Domain ... entities behaviors functions (Type => Type) algebraic data type エンティティは代数的データ型 Saturday, 30 January 16
  29. 29. Bank Account Trade Customer ... ... ... do trade process execution place order Solution Domain ... market regulations tax laws brokerage commission rates ... entities behaviors laws functions (Type => Type) algebraic data type business rules / invariants 法則はビジネス・ルールもしくは不変関係 Saturday, 30 January 16
  30. 30. Bank Account Trade Customer ... ... ... do trade process execution place order Solution Domain ... market regulations tax laws brokerage commission rates ... entities behaviors laws functions (Type => Type) algebraic data type business rules / invariants Monoid Monad ... モノイドやモナドといった型クラス Saturday, 30 January 16
  31. 31. Bank Account Trade Customer ... ... ... do trade process execution place order Solution Domain ... market regulations tax laws brokerage commission rates ... entities behaviors laws functions (Type => Type) algebraic data type business rules / invariants Monoid Monad ... これを全部やるとドメイン代数 Domain Algebra Saturday, 30 January 16
  32. 32. Domain Model = ∪(i) Bounded Context(i) Bounded Context = { f(x) | p(x) ∈ Domain Rules } • domain function • on an object of type x • composes with other functions • closed under composition • business rules Domain Algebra Domain Algebra 「境界づけられたコンテキスト」はドメイン代数のこと Saturday, 30 January 16
  33. 33. Client places order - flexible format 1 クライアントが注文を出す フォーマットは様々 Saturday, 30 January 16
  34. 34. Client places order - flexible format Transform to internal domain model entity and place for execution 1 2 内部でのドメインモデルエンティティに変換して、 実際に注文を出す Saturday, 30 January 16
  35. 35. Client places order - flexible format Transform to internal domain model entity and place for execution Trade & Allocate to client accounts 1 2 3 取引し、結果をクライアントのアカウントに紐づける Saturday, 30 January 16
  36. 36. def clientOrders: ClientOrderSheet => List[Order] def execute: Market => Account => Order => List[Execution] def allocate: List[Account] => Execution => List[Trade] Saturday, 30 January 16
  37. 37. def clientOrders: ClientOrderSheet => List[Order] def execute[Account <: BrokerAccount]: Market => Account => Order => List[Execution] def allocate[Account <: TradingAccount]: List[Account] => Execution => List[Trade] Saturday, 30 January 16
  38. 38. def clientOrders: ClientOrderSheet => List[Order] def execute: Market => Account => Order => List[Execution] def allocate: List[Account] => Execution => List[Trade] Types out of thin air No implementation till now Type names resonate domain language どこからともなく降ってきた型。今の所実装の話はゼロ。 型の名前はドメイン言語を反映 Saturday, 30 January 16
  39. 39. def clientOrders: ClientOrderSheet => List[Order] def execute: Market => Account => Order => List[Execution] def allocate: List[Account] => Execution => List[Trade] •Types (domain entities) • Functions operating on types (domain behaviors) • Laws (business rules) 型 (エンティティ)、関数 (ドメインの振る舞い)、 法則 (ビジネス・ルール) Saturday, 30 January 16
  40. 40. def clientOrders: ClientOrderSheet => List[Order] def execute: Market => Account => Order => List[Execution] def allocate: List[Account] => Execution => List[Trade] •Types (domain entities) • Functions operating on types (domain behaviors) • Laws (business rules) Algebra of the API これが API の代数 Saturday, 30 January 16
  41. 41. trait Trading[Account, Trade, ClientOrderSheet, Order, Execution, Market] { def clientOrders: ClientOrderSheet => List[Order] def execute: Market => Account => Order => List[Execution] def allocate: List[Account] => Execution => List[Trade] def tradeGeneration(market: Market, broker: Account, clientAccounts: List[Account]) = ??? } parameterized on typesmodule モジュール、型パラメータ Saturday, 30 January 16
  42. 42. Algebraic Design • The algebra is the binding contract of the API • Implementation is NOT part of the algebra • An algebra can have multiple interpreters (aka implementations) • One of the core principles of functional programming is to decouple the algebra from the interpreter 代数的設計手法: 代数は API が準拠する制約 実装は代数に含まれず、実装からは分離されている Saturday, 30 January 16
  43. 43. def clientOrders: ClientOrderSheet => List[Order] def execute: Market => Account => Order => List[Execution] def allocate: List[Account] => Execution => List[Trade] let’s do some algebra .. 代数の練習 Saturday, 30 January 16
  44. 44. def clientOrders: ClientOrderSheet => List[Order] def execute(m: Market, broker: Account): Order => List[Execution] def allocate(accounts: List[Account]): Execution => List[Trade] let’s do some algebra .. Saturday, 30 January 16
  45. 45. def clientOrders: ClientOrderSheet => List[Order] def execute(m: Market, broker: Account): Order => List[Execution] def allocate(accounts: List[Account]): Execution => List[Trade] let’s do some algebra .. Saturday, 30 January 16
  46. 46. def clientOrders: ClientOrderSheet => List[Order] def execute(m: Market, broker: Account): Order => List[Execution] def allocate(accounts: List[Account]): Execution => List[Trade] let’s do some algebra .. Saturday, 30 January 16
  47. 47. def clientOrders: ClientOrderSheet => List[Order] def execute(m: Market, broker: Account): Order => List[Execution] def allocate(accounts: List[Account]): Execution => List[Trade] let’s do some algebra .. Saturday, 30 January 16
  48. 48. def clientOrders: ClientOrderSheet => List[Order] def execute(m: Market, broker: Account): Order => List[Execution] def allocate(accounts: List[Account]): Execution => List[Trade] let’s do some algebra .. Saturday, 30 January 16
  49. 49. def f: A => List[B] def g: B => List[C] def h: C => List[D] .. a problem of composition .. これは ... 合成の問題だ Saturday, 30 January 16
  50. 50. .. a problem of composition with effects .. def f: A => List[B] def g: B => List[C] def h: C => List[D] これは ... 作用付きの合成の問題だ Saturday, 30 January 16
  51. 51. def f[M: Monad]: A => M[B] def g[M: Monad]: B => M[C] def h[M: Monad]: C => M[D] .. a problem of composition with effects that can be generalized .. これはモナドとして抽象化できる作用付きの合成の問題だ Saturday, 30 January 16
  52. 52. case class Kleisli[M[_], A, B](run: A => M[B]) { def andThen[C](f: B => M[C]) (implicit M: Monad[M]): Kleisli[M, A, C] = Kleisli((a: A) => M.flatMap(run(a))(f)) } .. function composition with Effects .. It’s a Kleisli ! 作用付きの関数の合成と言えば、Kleisli! Saturday, 30 January 16
  53. 53. def clientOrders: Kleisli[List, ClientOrderSheet, Order] def execute(m: Market, b: Account): Kleisli[List, Order, Execution] def allocate(acts: List[Account]): Kleisli[List, Execution, Trade] Follow the types .. function composition with Effects .. def clientOrders: ClientOrderSheet => List[Order] def execute(m: Market, broker: Account): Order => List[Execution] def allocate(accounts: List[Account]): Execution => List[Trade] 型に任せて考える Saturday, 30 January 16
  54. 54. def clientOrders: Kleisli[List, ClientOrderSheet, Order] def execute(m: Market, b: Account): Kleisli[List, Order, Execution] def allocate(acts: List[Account]): Kleisli[List, Execution, Trade] Domain algebra composed with the categorical algebra of a Kleisli Arrow .. function composition with Effects .. Klieisli 射によって合成されたドメイン代数 Saturday, 30 January 16
  55. 55. def clientOrders: Kleisli[List, ClientOrderSheet, Order] def execute(m: Market, b: Account): Kleisli[List, Order, Execution] def allocate(acts: List[Account]): Kleisli[List, Execution, Trade] .. that implements the semantics of our domain algebraically .. .. function composition with Effects .. ドメインの意味論を代数的に実装する作用付きの関数の合成 Saturday, 30 January 16
  56. 56. def tradeGeneration( market: Market, broker: Account, clientAccounts: List[Account]) = { clientOrders andThen execute(market, broker) andThen allocate(clientAccounts) } Implementation follows the specification .. the complete trade generation logic .. 実装は仕様に従う Saturday, 30 January 16
  57. 57. def tradeGeneration( market: Market, broker: Account, clientAccounts: List[Account]) = { clientOrders andThen execute(market, broker) andThen allocate(clientAccounts) } Implementation follows the specification and we get the Ubiquitous Language for free :-) .. the complete trade generation logic .. 実装は仕様に従い、 そこからユビキタス言語を読み取ることが出来る Saturday, 30 January 16
  58. 58. algebraic & functional • Just Pure Functions. Lower cognitive load - don’t have to think of the classes & data members where behaviors will reside • Compositional. Algebras compose - we defined the algebras of our domain APIs in terms of existing, time tested algebras of Kleislis and Monads 代数的かつ関数型の設計は、 純粋関数のみで構成する、合成可能な設計 Saturday, 30 January 16
  59. 59. def clientOrders: Kleisli[List, ClientOrderSheet, Order] def execute(m: Market, b: Account): Kleisli[List, Order, Execution] def allocate(acts: List[Account]): Kleisli[List, Execution, Trade] .. our algebra still doesn’t handle errors that may occur within our domain behaviors .. .. function composition with Effects .. そう言えばエラー処理どうする? Saturday, 30 January 16
  60. 60. more algebra, more types 代数と型、大盛りで追加! Saturday, 30 January 16
  61. 61. def clientOrders: Kleisli[List, ClientOrderSheet, Order] return type constructor List は戻り値の型コンストラクタ Saturday, 30 January 16
  62. 62. def clientOrders: Kleisli[List, ClientOrderSheet, Order] return type constructor What happens in case the operation fails ? 演算が失敗したらどうなる? Saturday, 30 January 16
  63. 63. Error handling as an Effect • pure and functional • with an explicit and published algebra • stackable with existing effects def clientOrders: Kleisli[List, ClientOrderSheet, Order] モナド作用としてのエラー処理 純粋で関数型に。明示的な代数。既存の作用と積み上げ可能。 Saturday, 30 January 16
  64. 64. def clientOrders: Kleisli[List, ClientOrderSheet, Order] .. stacking of effects .. M[List[_]] 作用の積み上げ Saturday, 30 January 16
  65. 65. def clientOrders: Kleisli[List, ClientOrderSheet, Order] .. stacking of effects .. M[List[_]]: M is a Monad List をエラー処理のためのモナド M で囲む Saturday, 30 January 16
  66. 66. type Response[A] = String / Option[A] val count: Response[Int] = some(10).right for { maybeCount <- count } yield { for { c <- maybeCount // use c } yield c } Monad Transformers モナド変換子 Saturday, 30 January 16
  67. 67. type Response[A] = String / Option[A] val count: Response[Int] = some(10).right for { maybeCount <- count } yield { for { c <- maybeCount // use c } yield c } type Error[A] = String / A type Response[A] = OptionT[Error, A] val count: Response[Int] = 10.point[Response] for{ c <- count // use c : c is an Int here } yield (()) Monad Transformers Saturday, 30 January 16
  68. 68. type Response[A] = String / Option[A] val count: Response[Int] = some(10).right for { maybeCount <- count } yield { for { c <- maybeCount // use c } yield c } type Error[A] = String / A type Response[A] = OptionT[Error, A] val count: Response[Int] = 10.point[Response] for{ c <- count // use c : c is an Int here } yield (()) Monad Transformers richer algebra 代数として扱いやすいのは OptionT を使った方 Saturday, 30 January 16
  69. 69. Monad Transformers • collapses the stack and gives us a single monad to deal with • order of stacking is important though モナド変換子は積み上げたモナドを一つに潰すことができる ただし積み上げる順番は大切 Saturday, 30 January 16
  70. 70. def clientOrders: Kleisli[List, ClientOrderSheet, Order] .. stacking of effects .. case class ListT[M[_], A] (run: M[List[A]]) { //.. ListT モナド変換子を使う Saturday, 30 January 16
  71. 71. これは代数にとって小さな一歩だが、 ドメインモデルにとっては巨大な跳躍である Saturday, 30 January 16
  72. 72. type StringOr[A] = String / A type Valid[A] = ListT[StringOr, A] これは代数にとって小さな一歩だが、 ドメインモデルにとっては巨大な跳躍である Saturday, 30 January 16
  73. 73. type StringOr[A] = String / A type Valid[A] = ListT[StringOr, A] def clientOrders: Kleisli[Valid, ClientOrderSheet, Order] def execute(m: Market, b: Account): Kleisli[Valid, Order, Execution] def allocate(acts: List[Account]): Kleisli[Valid, Execution, Trade] これは代数にとって小さな一歩だが、 ドメインモデルにとっては巨大な跳躍である Saturday, 30 January 16
  74. 74. type StringOr[A] = String / A type Valid[A] = ListT[StringOr, A] def clientOrders: Kleisli[Valid, ClientOrderSheet, Order] def execute(m: Market, b: Account): Kleisli[Valid, Order, Execution] def allocate(acts: List[Account]): Kleisli[Valid, Execution, Trade] .. a small change in algebra, a huge step for our domain model .. これは代数にとって小さな一歩だが、 ドメインモデルにとっては巨大な跳躍である Saturday, 30 January 16
  75. 75. def execute(market: Market, brokerAccount: Account) = kleisli[List, Order, Execution] { order => order.items.map { item => Execution(brokerAccount, market, ..) } } Saturday, 30 January 16
  76. 76. private def makeExecution(brokerAccount: Account, item: LineItem, market: Market): String / Execution = //.. def execute(market: Market, brokerAccount: Account) = kleisli[Valid, Order, Execution] { order => listT[StringOr]( order.items.map { item => makeExecution(brokerAccount, market, ..) }.sequenceU ) } Saturday, 30 January 16
  77. 77. List (aggregates) Algebra of types 型の代数 集約のための List Saturday, 30 January 16
  78. 78. List (aggregates) Disjunction (error accumulation) Algebra of types エラー蓄積のためのDisjunction Saturday, 30 January 16
  79. 79. List (aggregates) Disjunction (error accumulation) Kleisli (dependency injection) Algebra of types 依存性注入のための Kleisli Saturday, 30 January 16
  80. 80. List (aggregates) Disjunction (error accumulation) Kleisli (dependency injection) Future (reactive non-blocking computation) Algebra of types リアクティブでノンブロッキングな処理のための Future Saturday, 30 January 16
  81. 81. List (aggregates) Disjunction (error accumulation) Kleisli (dependency injection) Future (reactive non-blocking computation) Algebra of types Monad モナド Saturday, 30 January 16
  82. 82. List (aggregates) Disjunction (error accumulation) Kleisli (dependency injection) Future (reactive non-blocking computation) Algebra of types Monad Monoid モノイド Saturday, 30 January 16
  83. 83. List (aggregates) Disjunction (error accumulation) Kleisli (dependency injection) Future (reactive non-blocking computation) Algebra of types Monad Monoid Compositional 合成可能 Saturday, 30 January 16
  84. 84. List (aggregates) Disjunction (error accumulation) Kleisli (dependency injection) Future (reactive non-blocking computation) Algebra of types Monad Monoid Offers a suite of functional combinators さまざまな関数型コンビネータを提供する Saturday, 30 January 16
  85. 85. List (aggregates) Disjunction (error accumulation) Kleisli (dependency injection) Future (reactive non-blocking computation) Algebra of types Monad Monoid Handles edge cases so your domain logic remains clean ドメインロジックを綺麗保てるように、 エッジケースはこっちで処理する Saturday, 30 January 16
  86. 86. List (aggregates) Disjunction (error accumulation) Kleisli (dependency injection) Future (reactive non-blocking computation) Algebra of types Monad Monoid Implicitly encodes quite a bit of domain rules 暗黙的にかなり多くのドメインルールをエンコードする Saturday, 30 January 16
  87. 87. def clientOrders: Kleisli[List, ClientOrderSheet, Order] def execute(m: Market, b: Account): Kleisli[List, Order, Execution] def allocate(acts: List[Account]): Kleisli[List, Execution, Trade] .. the algebra .. 代数的な考え方 Saturday, 30 January 16
  88. 88. def clientOrders: Kleisli[List, ClientOrderSheet, Order] def execute(m: Market, b: Account): Kleisli[List, Order, Execution] def allocate(acts: List[Account]): Kleisli[List, Execution, Trade] .. the algebra .. functions 関数 Saturday, 30 January 16
  89. 89. .. the algebra .. def clientOrders: Kleisli[List, ClientOrderSheet, Order] def execute(m: Market, b: Account): Kleisli[List, Order, Execution] def allocate(acts: List[Account]): Kleisli[List, Execution, Trade] types 型 Saturday, 30 January 16
  90. 90. .. the algebra .. composition def tradeGeneration(market: Market, broker: Account, clientAccounts: List[Account]) = { clientOrders andThen execute(market, broker) andThen allocate(clientAccounts) } 合成 Saturday, 30 January 16
  91. 91. .. the algebra .. trait OrderLaw { def sizeLaw: Seq[ClientOrder] => Seq[Order] => Boolean = { cos => orders => cos.size == orders.size } def lineItemLaw: Seq[ClientOrder] => Seq[Order] => Boolean = { cos => orders => cos.map(instrumentsInClientOrder).sum == orders.map(_.items.size).sum } } laws of the algebra (domain rules) 代数の法則 Saturday, 30 January 16
  92. 92. Domain Rules as Algebraic Properties • part of the abstraction • equally important as the actual abstraction • verifiable as properties 代数的プロパティとしてのドメインルール プロパティとして検証可能となる Saturday, 30 January 16
  93. 93. .. domain rules verification .. property("Check Client Order laws") = forAll((cos: Set[ClientOrder]) => { val orders = for { os <- clientOrders.run(cos.toList) } yield os sizeLaw(cos.toSeq)(orders) == true lineItemLaw(cos.toSeq)(orders) == true }) property based testing FTW .. プロパティベーステスト最強 Saturday, 30 January 16
  94. 94. https://www.manning.com/books/functional-and-reactive- domain-modeling 本書いてます Saturday, 30 January 16
  95. 95. ThankYou! Saturday, 30 January 16

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