![]() ![]() A sender of an asynchronous message continues to execute after sending the message, whereas a sender of a synchronous message waits until it receives a reply from the receiver that it has completed its processing of the message before continuing execution.Īsynchronous messages correspond to either the sending of a signal or to an asynchronous invocation (or call) of an operation. The two basic kinds of messages are asynchronous and synchronous. Rick Steiner, in A Practical Guide to SysML (Third Edition), 2015 10.5.1 Synchronous and Asynchronous Messages In the rare case that both the parameter name and assigned feature are required, then the following syntax is used: As with input arguments, output arguments can be preceded by their corresponding parameter followed by an equal sign. The feature to which the return value is assigned is shown before the message name, followed by an equal sign. Output arguments associated with the message are shown in parentheses after the message name, and the return value, if any, is shown after the argument list. Īn open arrowhead on a dashed line shows a reply message.The notation for arguments is the same as for asynchronous messages. Ī closed arrowhead means a synchronous message.If this notation is not used, then all the input arguments must be listed in the appropriate order. The operation parameter or signal attribute name may be shown followed by an equal sign before an argument. Input arguments associated with the message are shown in parentheses, as a comma-separated list, after the message name. Īn open arrowhead means an asynchronous message.The shape of the arrowhead and the line style of the arrow line indicate the nature of the message as follows: The nonarrow (tail) end represents the occurrence corresponding to the sending of the message, and the arrow end represents the occurrence corresponding to the receipt of the message. Messages are represented by arrows between lifelines. As one might expect, the sending occurrence has to happen before the receiving occurrence. The actual sending of a message implies two occurrences: One is related to a send message event that happens to the instance corresponding to the sending lifeline the other is related to a receive message event that happens to the instance corresponding to the receiving lifeline. A feature can either be an attribute of the receiving lifeline or a local attribute or parameter of the receiver's current execution. When an operation returns a value, the features to which the output parameters and return value is assigned can be indicated. A reply message can include arguments that correspond to output parameters or the return value of the operation called. Arguments can be literal values, such as numbers or strings attributes of the part represented by the lifeline or parameters of the currently executing behavior. See Chapter 6 for a description of the behavioral features of blocks.Ĭall and send messages can include arguments that correspond to the input parameters of the associated operation or attributes of the associated send signal. In this case, the reply to the sender is indicated using a separate (optional) message from the receiver back to the sender. A synchronous message corresponds to the synchronous invocation of an operation. Signals are handled by receptions that are part of the definition of a block or interface. A signal is a definition of messages passed asynchronously between objects. A sender of an asynchronous message continues to execute immediately after sending the message, whereas a sender of a synchronous message waits until it receives a reply from the receiver that it has completed its processing of the message before continuing execution.Īsynchronous messages correspond to either the sending of a signal or to an asynchronous invocation (or call) of an operation. The two basic types of messages are asynchronous and synchronous. Rick Steiner, in Practical Guide to SysML, 2008 9.5.1 Synchronous and Asynchronous Messages ![]() Modeling Message-Based Behavior with Interactions ![]()
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