Proposals

ARO Language Specification

This directory contains the complete ARO (Action-Result-Object) language specification.

Reading Order

For newcomers to ARO, read the proposals in order:

#	Proposal	Topics
1	Language Fundamentals	Core syntax, literals, expressions, scoping
2	Control Flow	When guards, match expressions, iteration
3	Type System	Types, OpenAPI integration, schemas
4	Actions	Action roles, built-in actions, extensions
5	Application Architecture	App structure, lifecycle, concurrency
6	Error Philosophy	"Code is the error message"
7	Events & Reactive	Events, state, repositories
8	I/O Services	HTTP, files, sockets, system objects
9	Native Compilation	LLVM, aro build
10	Advanced Features	Regex, dates, exec
14	Domain Modeling	DDD patterns, entities, aggregates
15	Testing Framework	Colocated tests, Given/When/Then
16	Interoperability	External services, Call action
18	Data Pipelines	Filter, transform, aggregate collections
19	Standard Library	Primitive types, utilities
30	IDE Integration	Syntax highlighting, snippets
34	Language Server Protocol	LSP server, diagnostics, navigation
46	Typed Event Extraction	Schema-validated event extraction

Quick Reference

Core Language

ARO Statement:    Action [article] <result: qualifier> preposition [article] <object: qualifier>.
Feature Set:      (Name: Business Activity) { ... }
Publish:          Publish as <alias> <variable>.

Control Flow

Guard:            Action ... when <condition>.
Match:            match <value> { case <pattern> { ... } otherwise { ... } }
Iteration:        for each <item> in <collection> { ... }

Actions by Role

Role	Actions
REQUEST	Extract, Retrieve, Fetch, Read, List, Stat, Exists
OWN	Compute, Validate, Transform, Create, Update, Filter, Sort
RESPONSE	Return, Throw, Log, Send, Write
EXPORT	Publish, Store, Emit
SERVER	Start, Stop, Listen, Keepalive, Watch

I/O Syntax

Sink:             Log "message" to the <console>.
Source:           Read the <data> from the <file: "path">.
HTTP:             Request the <response> from the <url>.

Directory Structure

Proposals/
├── ARO-0001-language-fundamentals.md
├── ARO-0002-control-flow.md
├── ARO-0003-type-system.md
├── ARO-0004-actions.md
├── ARO-0005-application-architecture.md
├── ARO-0006-error-philosophy.md
├── ARO-0007-events-reactive.md
├── ARO-0008-io-services.md
├── ARO-0009-native-compilation.md
├── ARO-0010-advanced-features.md
├── ARO-0014-domain-modeling.md
├── ARO-0015-testing-framework.md
├── ARO-0016-interoperability.md
├── ARO-0018-query-language.md
├── ARO-0019-standard-library.md
├── ARO-0030-ide-integration.md
├── ARO-0034-language-server-protocol.md
└── ARO-0046-typed-event-extraction.md

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Last updated: January 2026