Items#

Role in SysML v2#

An item definition is a kind of occurrence definition for identifiable objects that may flow through a system or be acted on over time — for example data, signals, or fluids. A part is a specialized kind of item.

An item usage is a usage of one or more item definitions. Items are often used as port payloads and as event data in state machines.

Mapping to C++#

Item definitions are translated to C++ structs or classes in the generated code. Item usages become members of the enclosing part (or nested item). Multiplicity maps to arrays or constrained collections.

Example#

SysML v2 source code:

private import ScalarValues::*;

package Test {

    enum def EnumEvent {
        evA;
        evB;
        evC;
    }

    item def TxItem {
        attribute evt : EnumEvent;
        attribute data : Integer default 5;
    }

    port def MyPort {
        in item ev : TxItem;
    }

    part def Host {
        item scenario : TxItem[0..5];

        action def fill {
            assign scenario#(1).data := 100;
        }
    }
}

Items on ports are typically read with an accept in an action:

action def getMsg {
    action accept m:TxItem via recvPort {
        assign msg := m.evt;
    }
}

See also States, Ports, and the 7.2 release notes.