EMA-Kotlin

EMA-Kotlin is a Kotlin/JVM implementation of the Expressive and Modular Activation (EMA) mechanism for Context-Oriented Programming (COP). This implementation is inspired by and extends the ideas presented in the EMA paper and EMA-js reference implementation.

Status

• Core runtime implemented in Kotlin (Signal, SignalComp, Layer, EMA, partial methods, proceed).
• EMA-js behavior ported to Kotlin tests.
• Public playground included under docs/ with multiple Kotlin examples.
• GitHub Pages workflow included for automatic playground deployment.

Highlights

• Signal-driven activation with declarative condition expressions.
• Higher-order and recursive signal compositions.
• Dynamic layer deployment / undeployment.
• Partial method adaptation with Layer.proceed(...).
• Layer enter/exit hooks and adaptation conflict scenarios.

Build & Test

./gradlew test --no-daemon

Current suite:

• 82 tests
• Includes Kotlin ports of EMA-js tests + additional coverage tests

NPM Package

• Package: ema-kotlin
• Repository: https://github.com/pleger/EMA-Kotlin

Citation (APA)

Leger, P., Cardozo, N., & Masuhara, H. (2023). An expressive and modular layer activation mechanism for Context-Oriented Programming. Information and Software Technology, 156, 107132. https://doi.org/10.1016/j.infsof.2022.107132

Quick Start

import org.emakotlin.*

fun main() {
    EMA.init()

    val player = DynamicObject().apply {
        set("energy", Signal(0))
        defineMethod("speed") { 10 }
    }

    val turboLayer = LayerSpec(
        condition = SignalComp("e > 30")
    )

    EMA.exhibit(player, mapOf("e" to player.get<Signal>("energy")))
    EMA.addPartialMethod(turboLayer, player, "speed") {
        val base = Layer.proceed() as Int
        base + 7
    }

    println(player.call("speed")) // 10
    EMA.deploy(turboLayer)

    player.get<Signal>("energy").mutableValue = 40
    println(player.call("speed")) // 17
}

Core API

• Signal(initialValue, id = "_")
• SignalComp(expression, signals = emptyList(), id = "_")
• LayerSpec(condition, enter, exit, name)
• EMA.deploy(layerSpec) / EMA.undeploy(layerSpec)
• EMA.exhibit(target, mapOf("id" to signal))
• EMA.addPartialMethod(layerSpec, targetObj|listOfObjs, methodName) { ... }
• Layer.proceed(vararg args)

Playground

• Static site: docs/index.html
• Deploys through: .github/workflows/pages.yml
• Intended public URL (after enabling Pages):
  • https://pleger.github.io/EMA-Kotlin/

Playground examples included:

1. Signal composition
2. Enter/exit transitions
3. Partial method + proceed
4. Recursive context state

Project Structure

• src/main/kotlin/org/emakotlin/: EMA-Kotlin runtime
• src/test/kotlin/org/emakotlin/: translated EMA-js tests + extra tests
• docs/: playground and examples for GitHub Pages

Compatibility Notes

• Designed for Kotlin/JVM.
• Uses Gradle wrapper and JDK 21 toolchain defaults in gradle.properties.

Related

• EMA-js reference implementation: https://github.com/pragmaticslaboratory/EMAjs
• AspectScript playground inspiration: https://pleger.github.io/aspectscript

License

MIT (see LICENSE).