Collaborative state machine-related constructs are described below.

CollaborativeStateMachine

Within CSM, state machines are inspired by David Harel's statecharts. Their primary role is to exhibit autonomous, reactive behavior through state transitions. Actions can occur during transitions, upon entering or exiting a state, or while residing in a state. These actions may include invoking computational services, manipulating data, or raising events.

A collaborative state machine extends beyond single state machines by modeling an application as a collection of one or more state machines distributed across the computing continuum. State machines collaborate by raising and handling events and by sharing data. CSM defines a data model that includes persistent, local, and static data. Local and persistent data are declared through variables. Data declared within a component description is lexically declared, meaning it is created as part of the description itself, rather than dynamically generated through actions (see data model). Variable values are determined by evaluating expressions.

The memory mode defines how state machines may be distributed across the computing continuum. A collaborative state machine operates in one of two memory modes: shared or distributed. In shared memory mode, all state machines reside on the same computing resource and share memory. In distributed memory mode, state machines can execute on separate resources, each with private memory. These components run on a distributed computing infrastructure.

Single state machines always operate in shared memory mode.

Choosing between distributed and shared memory modes has significant implications. Distributed memory enables greater parallelism, scalability, replication, and decentralization, but may increase data transfer times when state machines on different resources need to exchange data.

For more details, see the data model description.

new CollaborativeStateMachine {
    name = "CSM"
    version = "2.0"
    memoryMode = "distributed"
    stateMachines {
        new StateMachine {...}...
    }
    localData = new Data {...}
    persistentData = new Data {...}
}

The following keywords can/must be provided:

name

The name keyword specifies the name of the collaborative state machine.

The name of the collaborative state machine is not referenced within the collaborative state machine and only serves to identify the collaborative state machine among other collaborative state machines.

version

The version keyword specifies the CSML version used within a description and is used to ensure backward-compatibility.

The CSML version is bound to a version of these specifications.

The version is a string enumeration and must be one of the following:

• 1.0
• 2.0
• 3.0

memoryMode

The memoryMode keyword specifies the memory mode of the complete collaborative state machine.

The memory mode applies to the entire collaborative state machine.

The memory mode is a string enumeration and must be one of the following:

• distributed
• shared

stateMachines

The stateMachines keyword is used to specify the collection of state machines included in the collaborative state machine.

localData / persistentData

The localData and persistentData keywords allow for lexically declaring respectively the local and persistent data of the collaborative state machine.

Depending on the memory mode of the collaborative state machine, either or both types of data will be accessible within the collaborative state machine, see dynamic extent.