# Metaprogramming / Language-Oriented Architecture > Every principle in this category is listed as a record. Page: Ontology · Principles Canonical: https://banes-lab.com/ontology#architecture-category-metaprogramming-language-oriented-architecture Listed in [Ontology · Principles](https://banes-lab.com/api/pages/ontology/principles.md), after [Metadata / Self-Description / Declarative Systems](https://banes-lab.com/ontology/principles/architecture-category-metadata-self-description-declarative-systems.md) and before [Model Architecture](https://banes-lab.com/ontology/principles/architecture-category-model-architecture.md). Every principle in this category is listed as a record. Each record carries its kind, its severity, the scopes it applies at and the layer it lives in, then the edge relations that join it to other records, the records that point back at it, the contracts that answer to it and the tensions it takes part in. The descriptors say how it is violated, detected, measured, repaired and enforced. Where the record carries one, an exemplar shows the shape before and after the principle is applied. Relations diagram The relations inside this category. ```mermaid flowchart LR n_homoiconicity["Homoiconicity"] n_code_as_data["Code as Data"] n_metaprogramming["Metaprogramming"] n_reflection["Reflection"] n_introspection["Introspection"] n_compile_time_evaluation["Compile-Time Evaluation"] n_runtime_code_generation["Runtime Code Generation"] n_domain_specific_language["Domain-Specific Language (DSL)"] n_language_oriented_programming["Language-Oriented Programming"] n_model_driven_architecture["Model-Driven Architecture"] n_homoiconicity --> n_metaprogramming n_code_as_data --> n_homoiconicity n_reflection --> n_introspection ``` ### Homoiconicity - Kind: [quality-attribute](https://banes-lab.com/records/kind/quality-attribute.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - Scope: language, metaprogramming - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition The degree to which a language represents its programs in its own data structures, so programs can be inspected and transformed as data. Requires [Code-as-Data Representation](https://banes-lab.com/records/lexicon/code-as-data-representation.md) Reinforces [Metaprogramming](https://banes-lab.com/records/architecture/metaprogramming.md) Enables [Macro Systems](https://banes-lab.com/records/lexicon/macro-systems.md), [DSLs](https://banes-lab.com/records/lexicon/dsls.md) In tension with [Readability](https://banes-lab.com/records/lexicon/readability.md) Conflicts with [Opaque Syntax Trees](https://banes-lab.com/records/lexicon/opaque-syntax-trees.md) Referenced by [Code as Data](https://banes-lab.com/records/architecture/code-as-data.md) Tensions [Homoiconicity / Readability](https://banes-lab.com/records/tension/homoiconicity-readability.md) Distinct from [Readability](https://banes-lab.com/records/lexicon/readability.md): Homoiconicity is programs held as data, while readability is how easily the developer reads the source that results. Violated by code transformed as strings where the language offers a code-as-data form Detected by language capability check Measured by macro/code-as-data usage Refactored by Use AST/DSL/Macro Representation Enforced by language/tooling constraints Refused by rules homoiconicity Before ```typescript function evaluateFoo(foo: Foo) { return foo.value * 2; } const fooRule = { operation: "multiply", operand: 2 }; ``` After ```typescript type Expr = | { op: "value"; key: keyof Foo } | { op: "const"; value: number } | { op: "multiply"; left: Expr; right: Expr }; const fooRule: Expr = { op: "multiply", left: { op: "value", key: "value" }, right: { op: "const", value: 2 } }; const result = evaluate(fooRule, foo); ``` How it is checked Checked by language/tooling constraints Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [Code-as-Data Representation](https://banes-lab.com/records/lexicon/code-as-data-representation.md), [Metaprogramming](https://banes-lab.com/records/architecture/metaprogramming.md), [Macro Systems](https://banes-lab.com/records/lexicon/macro-systems.md), [DSLs](https://banes-lab.com/records/lexicon/dsls.md) Shape it refuses [Opaque Syntax Trees](https://banes-lab.com/records/lexicon/opaque-syntax-trees.md) ### Code as Data - Kind: [principle](https://banes-lab.com/records/kind/principle.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - Scope: language, compiler, runtime - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition A design rule that logic to be generated or transformed is held as a typed data structure, such as a syntax tree, that tools can inspect and rewrite. Requires [AST or Data Representation](https://banes-lab.com/records/lexicon/ast-or-data-representation.md) Reinforces [Homoiconicity](https://banes-lab.com/records/architecture/homoiconicity.md), [Code Generation](https://banes-lab.com/records/lexicon/code-generation.md) Enables [Program Transformation](https://banes-lab.com/records/lexicon/program-transformation.md) In tension with [Safety/Debuggability](https://banes-lab.com/records/lexicon/safety-debuggability.md) Conflicts with [String-Based Code Generation](https://banes-lab.com/records/lexicon/string-based-code-generation.md) Tensions [Code as Data / Safety/Debuggability](https://banes-lab.com/records/tension/code-as-data-safety-debuggability.md) Violated by unsafe string eval/generation Detected by dynamic eval/string code construction Measured by unsafe eval count Refactored by Use AST Builder, Typed DSL Enforced by banned API rules Before ```typescript function fooRule(foo: Foo) { return foo.count > 3 && foo.active; } ``` After ```typescript const fooRule = { op: "and", args: [ { op: "gt", field: "count", value: 3 }, { op: "eq", field: "active", value: true }, ], } as const; executeRule(fooRule, foo); ``` How it is checked Checked by banned API rules Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [AST or Data Representation](https://banes-lab.com/records/lexicon/ast-or-data-representation.md), [Homoiconicity](https://banes-lab.com/records/architecture/homoiconicity.md), [Code Generation](https://banes-lab.com/records/lexicon/code-generation.md), [Program Transformation](https://banes-lab.com/records/lexicon/program-transformation.md) Shape it refuses [String-Based Code Generation](https://banes-lab.com/records/lexicon/string-based-code-generation.md) ### Metaprogramming - Kind: [technique](https://banes-lab.com/records/kind/technique.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - Scope: compile-time, runtime, framework - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition A technique for writing programs that generate or transform other programs, at compile time or at runtime. Requires [Reflection/AST/Code Generation](https://banes-lab.com/records/lexicon/reflection-ast-code-generation.md) Reinforces [Do Not Repeat Yourself (DRY)](https://banes-lab.com/records/architecture/duplicate-code.md), [DSLs](https://banes-lab.com/records/lexicon/dsls.md) Enables [Boilerplate Elimination](https://banes-lab.com/records/lexicon/boilerplate-elimination.md) In tension with [Debuggability](https://banes-lab.com/records/lexicon/debuggability.md), [Static Analysis](https://banes-lab.com/records/architecture/static-analysis.md), [Explicit Handwritten Code](https://banes-lab.com/records/lexicon/explicit-handwritten-code.md) Conflicts with none Referenced by [Homoiconicity](https://banes-lab.com/records/architecture/homoiconicity.md) Tensions [Metaprogramming / Debuggability](https://banes-lab.com/records/tension/debuggability-metaprogramming.md), [Metaprogramming / Static Analysis](https://banes-lab.com/records/tension/metaprogramming-static-analysis.md), [Metaprogramming / Explicit Handwritten Code](https://banes-lab.com/records/tension/explicit-handwritten-code-metaprogramming.md) Distinct from [DSLs](https://banes-lab.com/records/lexicon/dsls.md): Metaprogramming is code that writes or transforms code, while a domain-specific language is a notation for one domain, which metaprogramming can build. Violated by unsafe/opaque generated behavior Detected by dynamic generation without tests/schema Measured by generated code coverage, [complexity](https://banes-lab.com/records/reasoning/lens-complexity.md) Refactored by Add Generator Tests, Make Metadata Explicit Enforced by generator validation Before ```typescript class FooDto { id!: string; name!: string; } class BarDto { id!: string; name!: string; } ``` After ```typescript const entity = defineEntity({ id: string(), name: string() }); const FooDto = generateType("FooDto", entity); const BarDto = generateType("BarDto", entity); ``` How it is checked Checked by generator validation Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [Reflection/AST/Code Generation](https://banes-lab.com/records/lexicon/reflection-ast-code-generation.md), [Do Not Repeat Yourself (DRY)](https://banes-lab.com/records/architecture/duplicate-code.md), [DSLs](https://banes-lab.com/records/lexicon/dsls.md), [Boilerplate Elimination](https://banes-lab.com/records/lexicon/boilerplate-elimination.md) Shape it refuses Not answered ### Reflection - Kind: [mechanism](https://banes-lab.com/records/kind/mechanism.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - Scope: runtime, metadata, framework - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition A mechanism that lets a program read and act on type metadata about its own structure at runtime. Requires [Runtime Type Metadata](https://banes-lab.com/records/lexicon/runtime-type-metadata.md) Reinforces [Introspection](https://banes-lab.com/records/architecture/introspection.md), [Runtime Discovery](https://banes-lab.com/records/architecture/runtime-discovery.md) Enables [Dynamic Binding](https://banes-lab.com/records/architecture/dynamic-binding.md) In tension with [Performance/Safety](https://banes-lab.com/records/lexicon/performance-safety.md), [Static Analysis](https://banes-lab.com/records/architecture/static-analysis.md) Conflicts with none Tensions [Reflection / Performance/Safety](https://banes-lab.com/records/tension/performance-safety-reflection.md), [Reflection / Static Analysis](https://banes-lab.com/records/tension/reflection-static-analysis.md) Distinct from [Dynamic Binding](https://banes-lab.com/records/architecture/dynamic-binding.md): Reflection reads type metadata at runtime, while dynamic binding selects an implementation at runtime, with or without reflection. Distinct from [Introspection](https://banes-lab.com/records/architecture/introspection.md): Introspection only reads a type and its members, while reflection also acts on what it reads. Distinct from [Static Analysis](https://banes-lab.com/records/architecture/static-analysis.md): Reflection inspects structure while the program runs, while static analysis inspects source without running it. Violated by reflection used to bypass contracts/visibility Detected by reflective access to internals Measured by unsafe reflection count Refactored by Replace with Explicit Interface/Metadata Enforced by lint/security rules Before ```typescript const fields = ["id", "name", "count"]; for (const field of fields) renderField(foo[field]); ``` After ```typescript for (const [field, metadata] of reflect(FooSchema).entries()) { renderField(field, metadata, foo[field]); } ``` How it is checked Checked by lint/security rules Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [Runtime Type Metadata](https://banes-lab.com/records/lexicon/runtime-type-metadata.md), [Introspection](https://banes-lab.com/records/architecture/introspection.md), [Runtime Discovery](https://banes-lab.com/records/architecture/runtime-discovery.md), [Dynamic Binding](https://banes-lab.com/records/architecture/dynamic-binding.md) Shape it refuses Not answered ### Introspection - Kind: [mechanism](https://banes-lab.com/records/kind/mechanism.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - Scope: runtime, metadata - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition A mechanism that lets a program query an object's type and public members at runtime without changing them. Requires [Type Metadata](https://banes-lab.com/records/lexicon/type-metadata.md) Reinforces [Self-Describing Systems](https://banes-lab.com/records/lexicon/self-describing-systems.md) Enables [Discovery](https://banes-lab.com/records/lexicon/discovery.md), [Diagnostics](https://banes-lab.com/records/lexicon/diagnostics.md) In tension with [Encapsulation](https://banes-lab.com/records/architecture/encapsulation.md) Conflicts with [Opaque Runtime Behavior](https://banes-lab.com/records/architecture/opaque-runtime-behavior.md) Referenced by [Self-Describing Structures](https://banes-lab.com/records/architecture/self-describing-structures.md), [Reflection](https://banes-lab.com/records/architecture/reflection.md) Tensions [Introspection / Encapsulation](https://banes-lab.com/records/tension/encapsulation-introspection.md) Violated by relying on undocumented internal structure Detected by introspection of private internals Measured by introspection usage risk Refactored by Add Public Metadata API Enforced by API boundaries Before ```typescript function supportsExport(plugin: any) { try { plugin.exportFoo(foo); return true; } catch { return false; } } ``` After ```typescript function supportsExport(plugin: Plugin) { return introspect(plugin).methods.includes("exportFoo"); } ``` How it is checked Checked by API boundaries Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [Type Metadata](https://banes-lab.com/records/lexicon/type-metadata.md), [Self-Describing Systems](https://banes-lab.com/records/lexicon/self-describing-systems.md), [Discovery](https://banes-lab.com/records/lexicon/discovery.md), [Diagnostics](https://banes-lab.com/records/lexicon/diagnostics.md) Shape it refuses [Opaque Runtime Behavior](https://banes-lab.com/records/architecture/opaque-runtime-behavior.md), [Opaque Runtime Behavior](https://banes-lab.com/records/architecture/opaque-runtime-behavior.md) ### Compile-Time Evaluation - Kind: [mechanism](https://banes-lab.com/records/kind/mechanism.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - Scope: compiler, build - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition A mechanism that computes values, checks or generated code during the build, so the work and its errors happen before runtime. Requires [Compile-Time Inputs](https://banes-lab.com/records/lexicon/compile-time-inputs.md) Reinforces [Optimization](https://banes-lab.com/records/architecture/optimization.md), [Type Safety](https://banes-lab.com/records/architecture/type-safety.md) Enables [Early Error Detection](https://banes-lab.com/records/lexicon/early-error-detection.md) In tension with [Build Complexity](https://banes-lab.com/records/lexicon/build-complexity.md), [Runtime Dynamic Evaluation](https://banes-lab.com/records/lexicon/runtime-dynamic-evaluation.md) Conflicts with none Tensions [Compile-Time Evaluation / Build Complexity](https://banes-lab.com/records/tension/build-complexity-compile-time-evaluation.md), [Compile-Time Evaluation / Runtime Dynamic Evaluation](https://banes-lab.com/records/tension/compile-time-evaluation-runtime-dynamic-evaluation.md) Violated by runtime work that could be validated/generated at compile time Detected by repeated runtime reflection/validation Measured by compile-time coverage Refactored by Move Check/Generation to Compile Time Enforced by compiler plugins/build checks Before ```typescript const fooRoutes = buildRoutesAtStartup(fooRouteDefinitions); ``` After ```typescript const fooRoutes = compileTime(() => buildRoutes(fooRouteDefinitions)); export const routeTable = fooRoutes; ``` How it is checked Checked by compiler plugins/build checks Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [Compile-Time Inputs](https://banes-lab.com/records/lexicon/compile-time-inputs.md), [Optimization](https://banes-lab.com/records/architecture/optimization.md), [Type Safety](https://banes-lab.com/records/architecture/type-safety.md), [Early Error Detection](https://banes-lab.com/records/lexicon/early-error-detection.md) Shape it refuses Not answered ### Runtime Code Generation - Kind: [mechanism](https://banes-lab.com/records/kind/mechanism.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [discouraged](https://banes-lab.com/records/vocabulary/severity-discouraged.md) - Scope: runtime, framework - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition A mechanism that builds executable code while the program runs, from a specification such as a field mapping. Requires [Safe Generation Boundary](https://banes-lab.com/records/lexicon/safe-generation-boundary.md) Reinforces [Runtime Extensibility](https://banes-lab.com/records/architecture/runtime-extensibility.md) Enables [Dynamic Optimization/Adaptation](https://banes-lab.com/records/lexicon/dynamic-optimization-adaptation.md) In tension with [Security/Debugging](https://banes-lab.com/records/lexicon/security-debugging.md), [Static Safety](https://banes-lab.com/records/lexicon/static-safety.md) Conflicts with none Tensions [Runtime Code Generation / Security/Debugging](https://banes-lab.com/records/tension/runtime-code-generation-security-debugging.md), [Runtime Code Generation / Static Safety](https://banes-lab.com/records/tension/runtime-code-generation-static-safety.md) Violated by unsafe eval, untrusted code generation Detected by dynamic eval with external input Measured by unsafe generation paths Refactored by Use Safe Generator, Sandbox, Precompile Enforced by [security policy](https://banes-lab.com/records/algorithms/security-policy.md) Before ```typescript function mapFoo(row: any) { return { id: row["foo_id"], name: row["foo_name"], count: row["foo_count"] }; } ``` After ```typescript const mapFoo = generateMapper({ foo_id: "id", foo_name: "name", foo_count: "count", }); ``` How it is checked Checked by security policy Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [Safe Generation Boundary](https://banes-lab.com/records/lexicon/safe-generation-boundary.md), [Runtime Extensibility](https://banes-lab.com/records/architecture/runtime-extensibility.md), [Dynamic Optimization/Adaptation](https://banes-lab.com/records/lexicon/dynamic-optimization-adaptation.md) Shape it refuses Not answered ### Domain-Specific Language (DSL) - Kind: [pattern](https://banes-lab.com/records/kind/pattern.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - Scope: domain, configuration, rules - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition A design pattern that expresses a domain's rules or workflows in a small language with a defined grammar and a validator. Requires [Formal Grammar/Semantics](https://banes-lab.com/records/lexicon/formal-grammar-semantics.md) Reinforces [Declarative Configuration](https://banes-lab.com/records/architecture/declarative-configuration.md), [Ubiquitous Language](https://banes-lab.com/records/architecture/ubiquitous-language.md) Enables [Domain Expressiveness](https://banes-lab.com/records/lexicon/domain-expressiveness.md) In tension with [Tooling/Maintenance](https://banes-lab.com/records/lexicon/tooling-maintenance.md) Conflicts with [General-Purpose Boilerplate](https://banes-lab.com/records/lexicon/general-purpose-boilerplate.md) Tensions [Domain-Specific Language (DSL) / Tooling/Maintenance](https://banes-lab.com/records/tension/domain-specific-language-dsl-tooling-maintenance.md) Violated by ambiguous ad-hoc mini-language Detected by stringly-typed rules without parser/schema Measured by DSL validation coverage Refactored by Define Grammar, Add Parser/Validator Enforced by DSL tests, schema/grammar checks Before ```typescript createWorkflow([ { type: "validate", target: "foo" }, { type: "save", target: "foo" }, { type: "publish", target: "foo.created" }, ]); ``` After ```typescript fooWorkflow("create", flow => flow.validate(FooSchema) .save("FooStore") .publish("FooCreated") ); ``` How it is checked Checked by DSL tests, schema/grammar checks Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [Formal Grammar/Semantics](https://banes-lab.com/records/lexicon/formal-grammar-semantics.md), [Declarative Configuration](https://banes-lab.com/records/architecture/declarative-configuration.md), [Ubiquitous Language](https://banes-lab.com/records/architecture/ubiquitous-language.md), [Domain Expressiveness](https://banes-lab.com/records/lexicon/domain-expressiveness.md) Shape it refuses [General-Purpose Boilerplate](https://banes-lab.com/records/lexicon/general-purpose-boilerplate.md) ### Language-Oriented Programming - Kind: [approach](https://banes-lab.com/records/kind/approach.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - Scope: domain, platform, code generation - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition An approach in which each problem domain gets its own language, with a type checker and an evaluator, and solutions are written in it. Requires [DSLs](https://banes-lab.com/records/lexicon/dsls.md), [Code Generation or Interpreters](https://banes-lab.com/records/lexicon/code-generation-or-interpreters.md) Reinforces [Domain Modeling](https://banes-lab.com/records/lexicon/domain-modeling.md) Enables [High-Level Domain Expression](https://banes-lab.com/records/lexicon/high-level-domain-expression.md) In tension with [Toolchain Complexity](https://banes-lab.com/records/lexicon/toolchain-complexity.md), [One-Size General-Purpose Code](https://banes-lab.com/records/lexicon/one-size-general-purpose-code.md) Conflicts with none Tensions [Language-Oriented Programming / Toolchain Complexity](https://banes-lab.com/records/tension/language-oriented-programming-toolchain-complexity.md), [Language-Oriented Programming / One-Size General-Purpose Code](https://banes-lab.com/records/tension/language-oriented-programming-one-size-general-purpose-code.md) Distinct from [One-Size General-Purpose Code](https://banes-lab.com/records/lexicon/one-size-general-purpose-code.md): Language-oriented programming gives each domain its own language, while general-purpose code writes every domain in one language. Violated by proliferation of informal unvalidated DSLs Detected by multiple inconsistent rule/config syntaxes Measured by language consistency/tooling Refactored by Consolidate DSL, Add Tooling Enforced by grammar/schema validation Before ```typescript function processFoo(config: Record) { interpretAdHocConfig(config); } ``` After ```typescript const FooPolicyLanguage = defineLanguage({ expressions: ["field", "equals", "all", "any"], typeChecker: fooPolicyTypeChecker, evaluator: fooPolicyEvaluator, }); FooPolicyLanguage.run(fooPolicy, foo); ``` How it is checked Checked by grammar/schema validation Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [DSLs](https://banes-lab.com/records/lexicon/dsls.md), [Code Generation or Interpreters](https://banes-lab.com/records/lexicon/code-generation-or-interpreters.md), [Domain Modeling](https://banes-lab.com/records/lexicon/domain-modeling.md), [High-Level Domain Expression](https://banes-lab.com/records/lexicon/high-level-domain-expression.md) Shape it refuses Not answered ### Model-Driven Architecture - Kind: [approach](https://banes-lab.com/records/kind/approach.md) - Category: [Metaprogramming / Language-Oriented Architecture](https://banes-lab.com/ontology/principles/architecture-category-metaprogramming-language-oriented-architecture.md) - Severity: [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - Scope: system, code generation, domain model - Layer: [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) Details Definition An approach in which a formal model is the source of truth and the implementation is generated from it by transformation rules. Requires [Formal Model](https://banes-lab.com/records/lexicon/formal-model.md), [Transformation Rules](https://banes-lab.com/records/lexicon/transformation-rules.md) Reinforces [Metadata-Driven Design](https://banes-lab.com/records/architecture/metadata-driven-design.md) Enables [Generated Implementations](https://banes-lab.com/records/lexicon/generated-implementations.md) In tension with none Conflicts with [Handwritten Divergence](https://banes-lab.com/records/lexicon/handwritten-divergence.md) Distinct from [Metadata-Driven Design](https://banes-lab.com/records/architecture/metadata-driven-design.md): Model-driven architecture generates the implementation from a formal model by transformation rules, while metadata-driven design drives forms, routes or plugins from validated metadata. Violated by generated code manually edited/diverged Detected by model-code drift Measured by generation conformance Refactored by Regenerate, Lock Generated Files, Update Model Enforced by generation CI Before ```typescript class FooController {} class FooService {} class FooRepository {} class FooDto {} ``` After ```typescript const fooModel = defineModel({ entity: "Foo", fields: { id: "FooId", name: "string" }, operations: ["create", "read", "rename"], }); generateApplication(fooModel); ``` How it is checked Checked by generation CI Population Every generator, reflective access, evaluation site and language definition in the codebase Freshness A verdict stands until a generator, a grammar or the model it generates from changes Refusal The banned-API rule, the generator test or the grammar validation fails the change Observation Eval and reflection call sites read from source, and generated output compared with its model Evidence None, because the catalog states this check as a class, so a watched run belongs to each system that adopts it Authoritative side The model and the grammar, which generated output is derived from and compared against Depends on [Formal Model](https://banes-lab.com/records/lexicon/formal-model.md), [Transformation Rules](https://banes-lab.com/records/lexicon/transformation-rules.md), [Metadata-Driven Design](https://banes-lab.com/records/architecture/metadata-driven-design.md), [Generated Implementations](https://banes-lab.com/records/lexicon/generated-implementations.md) Shape it refuses [Handwritten Divergence](https://banes-lab.com/records/lexicon/handwritten-divergence.md) ## Links to - [quality-attribute](https://banes-lab.com/records/kind/quality-attribute.md) - [contextual](https://banes-lab.com/records/vocabulary/severity-contextual.md) - [Declarative Core](https://banes-lab.com/records/layer/declarative-core.md) - [Code-as-Data Representation](https://banes-lab.com/records/lexicon/code-as-data-representation.md) - [Metaprogramming](https://banes-lab.com/records/architecture/metaprogramming.md) - [Macro Systems](https://banes-lab.com/records/lexicon/macro-systems.md) - [DSLs](https://banes-lab.com/records/lexicon/dsls.md) - [Readability](https://banes-lab.com/records/lexicon/readability.md) - [Opaque Syntax Trees](https://banes-lab.com/records/lexicon/opaque-syntax-trees.md) - [Code as Data](https://banes-lab.com/records/architecture/code-as-data.md) - [Homoiconicity / Readability](https://banes-lab.com/records/tension/homoiconicity-readability.md) - [principle](https://banes-lab.com/records/kind/principle.md) - [AST or Data Representation](https://banes-lab.com/records/lexicon/ast-or-data-representation.md) - [Homoiconicity](https://banes-lab.com/records/architecture/homoiconicity.md) - [Code Generation](https://banes-lab.com/records/lexicon/code-generation.md) - [Program Transformation](https://banes-lab.com/records/lexicon/program-transformation.md) - [Safety/Debuggability](https://banes-lab.com/records/lexicon/safety-debuggability.md) - [String-Based Code Generation](https://banes-lab.com/records/lexicon/string-based-code-generation.md) - [Code as Data / Safety/Debuggability](https://banes-lab.com/records/tension/code-as-data-safety-debuggability.md) - [technique](https://banes-lab.com/records/kind/technique.md) - [Reflection/AST/Code Generation](https://banes-lab.com/records/lexicon/reflection-ast-code-generation.md) - [Do Not Repeat Yourself](https://banes-lab.com/records/architecture/duplicate-code.md) - [Boilerplate Elimination](https://banes-lab.com/records/lexicon/boilerplate-elimination.md) - [Debuggability](https://banes-lab.com/records/lexicon/debuggability.md) - [Static Analysis](https://banes-lab.com/records/architecture/static-analysis.md) - [Explicit Handwritten Code](https://banes-lab.com/records/lexicon/explicit-handwritten-code.md) - [Metaprogramming / Debuggability](https://banes-lab.com/records/tension/debuggability-metaprogramming.md) - [Metaprogramming / Static Analysis](https://banes-lab.com/records/tension/metaprogramming-static-analysis.md) - [Metaprogramming / Explicit Handwritten Code](https://banes-lab.com/records/tension/explicit-handwritten-code-metaprogramming.md) - [Complexity](https://banes-lab.com/records/reasoning/lens-complexity.md) - [mechanism](https://banes-lab.com/records/kind/mechanism.md) - [Runtime Type Metadata](https://banes-lab.com/records/lexicon/runtime-type-metadata.md) - [Introspection](https://banes-lab.com/records/architecture/introspection.md) - [Runtime Discovery](https://banes-lab.com/records/architecture/runtime-discovery.md) - [Dynamic Binding](https://banes-lab.com/records/architecture/dynamic-binding.md) - [Performance/Safety](https://banes-lab.com/records/lexicon/performance-safety.md) - [Reflection / Performance/Safety](https://banes-lab.com/records/tension/performance-safety-reflection.md) - [Reflection / Static Analysis](https://banes-lab.com/records/tension/reflection-static-analysis.md) - [Type Metadata](https://banes-lab.com/records/lexicon/type-metadata.md) - [Self-Describing Systems](https://banes-lab.com/records/lexicon/self-describing-systems.md) - [Discovery](https://banes-lab.com/records/lexicon/discovery.md) - [Diagnostics](https://banes-lab.com/records/lexicon/diagnostics.md) - [Encapsulation](https://banes-lab.com/records/architecture/encapsulation.md) - [Opaque Runtime Behavior](https://banes-lab.com/records/architecture/opaque-runtime-behavior.md) - [Self-Describing Structures](https://banes-lab.com/records/architecture/self-describing-structures.md) - [Reflection](https://banes-lab.com/records/architecture/reflection.md) - [Introspection / Encapsulation](https://banes-lab.com/records/tension/encapsulation-introspection.md) - [Compile-Time Inputs](https://banes-lab.com/records/lexicon/compile-time-inputs.md) - [Optimization](https://banes-lab.com/records/architecture/optimization.md) - [Type Safety](https://banes-lab.com/records/architecture/type-safety.md) - [Early Error Detection](https://banes-lab.com/records/lexicon/early-error-detection.md) - [Build Complexity](https://banes-lab.com/records/lexicon/build-complexity.md) - [Runtime Dynamic Evaluation](https://banes-lab.com/records/lexicon/runtime-dynamic-evaluation.md) - [Compile-Time Evaluation / Build Complexity](https://banes-lab.com/records/tension/build-complexity-compile-time-evaluation.md) - [Compile-Time Evaluation / Runtime Dynamic Evaluation](https://banes-lab.com/records/tension/compile-time-evaluation-runtime-dynamic-evaluation.md) - [discouraged](https://banes-lab.com/records/vocabulary/severity-discouraged.md) - [Safe Generation Boundary](https://banes-lab.com/records/lexicon/safe-generation-boundary.md) - [Runtime Extensibility](https://banes-lab.com/records/architecture/runtime-extensibility.md) - [Dynamic Optimization/Adaptation](https://banes-lab.com/records/lexicon/dynamic-optimization-adaptation.md) - [Security/Debugging](https://banes-lab.com/records/lexicon/security-debugging.md) - [Static Safety](https://banes-lab.com/records/lexicon/static-safety.md) - [Runtime Code Generation / Security/Debugging](https://banes-lab.com/records/tension/runtime-code-generation-security-debugging.md) - [Runtime Code Generation / Static Safety](https://banes-lab.com/records/tension/runtime-code-generation-static-safety.md) - [Security Policy](https://banes-lab.com/records/algorithms/security-policy.md) - [pattern](https://banes-lab.com/records/kind/pattern.md) - [Formal Grammar/Semantics](https://banes-lab.com/records/lexicon/formal-grammar-semantics.md) - [Declarative Configuration](https://banes-lab.com/records/architecture/declarative-configuration.md) - [Ubiquitous Language](https://banes-lab.com/records/architecture/ubiquitous-language.md) - [Domain Expressiveness](https://banes-lab.com/records/lexicon/domain-expressiveness.md) - [Tooling/Maintenance](https://banes-lab.com/records/lexicon/tooling-maintenance.md) - [General-Purpose Boilerplate](https://banes-lab.com/records/lexicon/general-purpose-boilerplate.md) - [Domain-Specific Language (DSL) / Tooling/Maintenance](https://banes-lab.com/records/tension/domain-specific-language-dsl-tooling-maintenance.md) - [approach](https://banes-lab.com/records/kind/approach.md) - [Code Generation or Interpreters](https://banes-lab.com/records/lexicon/code-generation-or-interpreters.md) - [Domain Modeling](https://banes-lab.com/records/lexicon/domain-modeling.md) - [High-Level Domain Expression](https://banes-lab.com/records/lexicon/high-level-domain-expression.md) - [Toolchain Complexity](https://banes-lab.com/records/lexicon/toolchain-complexity.md) - [One-Size General-Purpose Code](https://banes-lab.com/records/lexicon/one-size-general-purpose-code.md) - [Language-Oriented Programming / Toolchain Complexity](https://banes-lab.com/records/tension/language-oriented-programming-toolchain-complexity.md) - [Language-Oriented Programming / One-Size General-Purpose Code](https://banes-lab.com/records/tension/language-oriented-programming-one-size-general-purpose-code.md) - [Formal Model](https://banes-lab.com/records/lexicon/formal-model.md) - [Transformation Rules](https://banes-lab.com/records/lexicon/transformation-rules.md) - [Metadata-Driven Design](https://banes-lab.com/records/architecture/metadata-driven-design.md) - [Generated Implementations](https://banes-lab.com/records/lexicon/generated-implementations.md) - [Handwritten Divergence](https://banes-lab.com/records/lexicon/handwritten-divergence.md) ## Linked from - [The layer topology](https://banes-lab.com/ontology/schema/the-layer-topology.md) - [The membership](https://banes-lab.com/ontology/schema/the-membership.md)