Glossary

Area A namespace unit in Mélodium, materialized by a .mel file. Subareas are created by placing .mel files inside a folder with the parent area’s name. Elements within the same project are referenced using root/area::element or local/subarea::element. See: Project Organization

Block A port kind written Block<T> that carries exactly one value of type T. Used for single events, triggers, and configuration values. The name refers to a single block of data, not to suspending execution. See: Connections

Configuration parameter A parameter written in square brackets ([param: Type]) on a treatment declaration, used to pass a model instance or fixed resource into a treatment. Configuration parameters are always constant. See: Parameters

Connection A directed link from an output port to an input port, written with ->. Connections define the data flow between treatment instances inside a treatment body. A connection must link ports of the same type and kind, cannot create cycles, and a given input may only have one connection. See: Connections

Context Track-wide data prefixed with @, provided by a source treatment and implicitly available to any treatment in the same track that declares require @ContextName. Unlike parameters, contexts do not need to be explicitly passed down the call chain. See: Contexts

Entrypoint A named treatment that can be invoked directly from the command line to start a program. Declared in Compo.toml. The main entrypoint is called when no name is given. Treatment parameters become CLI arguments automatically. See: Entrypoints

Function A pure, side-effect-free callable prefixed with |, used to compute parameter values. Functions are executed once at program initialization when used as const parameters, or once per track creation when used as var parameters. See: Functions

Model A stateful element that lives for the entire program execution. Models are the sources of events and tracks: they are the starting points from which data enters the system. A model is declared by extending a library model and configuring its parameters. See: Models

Self A keyword used inside a treatment body to refer to the hosting treatment’s own input and output ports. Self.input_name and Self.output_name wire the treatment’s declared ports into its internal connection graph. See: Treatments

Stream A port kind written Stream<T> that carries a continuous, unbounded sequence of values of type T. The general case for data transmission in Mélodium. See: Connections

Track The complete set of treatment instances and connections created together from a single model event. Each event from a model spawns a new independent track. All tracks run concurrently, each with its own data and context. See: Tracks

Trait An intrinsic capability of a type, such as the ability to be added (Add), compared (PartialEquality), or converted to a string (ToString). Traits are used to constrain generic type parameters. See: Traits

Treatment The primary computation unit in Mélodium. A treatment declares inputs, outputs, and a body of other treatment instances connected together. Treatments do not execute line by line; all inner treatments run concurrently when data is available. See: Treatments

void A core type that carries no value. Block<void> is used as a trigger (signals that something happened), and Stream<void> is used as a continuation indicator (signals ongoing activity without conveying data). See: Core types