ATLExpression

protocol ATLExpression : Hashable, Sendable

Overview

ATL expressions form the computational foundation of the Atlas Transformation Language, providing a rich expression system built upon OCL (Object Constraint Language) with extensions for model transformation. Expressions are evaluated within execution contexts that provide access to source and target models, variables, and helper functions.

Overview

ATL expressions support multiple evaluation paradigms:

• Navigation expressions: Property access and reference traversal

• Operation calls: Method invocation on objects and collections

• Helper invocations: Custom function calls defined in ATL modules

• Literal values: Constants and primitive data

• Collection operations: OCL-style collection manipulation

• Conditional logic: If-then-else expressions for branching

Implementation Notes

All expressions conform to Sendable to enable safe concurrent evaluation within the ATL virtual machine’s actor-based architecture. Expression evaluation is asynchronous to support complex model traversals and transformation operations.

Example Usage

let navigationExpr = ATLNavigationExpression(
    source: ATLVariableExpression(name: "self"),
    property: "firstName"
)

let result = try await navigationExpr.evaluate(in: executionContext)