Message types in sequence diagrams

Dear All,

Could somebody explain (with examples if possible - the documentation is not helpful at all in this respect) how the different types of messages in sequence diagrams work - what is the difference for example between a send message and a call message? The documentation says very little, is not helpful and I am not sure at all this is standard UML.

Regards,
George

Hi George,

Thanks for your inquiry. We completely follow UML Specification v2.2, so the types of message are UML standard. If you want to have UML Specification v2.2, please visit:
http://www.omg.org/docs/formal/09-02-02.pdf

And we have a resources page about notation of sequence diagram at the following link, you can find information about different types of messages:
http://oldresources.visual-paradigm.com/uml_diagrams/sequence_diagram/sequence_diagram_notation.html

By the way, we have online courses in Online Training Center about UML modeling, you can take the free course of sequence diagram at the link below (you simply need to make a free subscription to take the free online courses):
https://www.vp-trainingcenter.com/summary/usingseqcommdiagram.html

I hope all these can answer your question and provide more information about sequence diagram. If you have any further inquiry, please feel free to ask.

Best regards,
Lilian Wong

[quote=LilianWong]Hi George,

Thanks for your inquiry. We completely follow UML Specification v2.2, so the types of message are UML standard. If you want to have UML Specification v2.2, please visit:
http://www.omg.org/docs/formal/09-02-02.pdf

And we have a resources page about notation of sequence diagram at the following link, you can find information about different types of messages:
http://oldresources.visual-paradigm.com/uml_diagrams/sequence_diagram/sequence_diagram_notation.html

By the way, we have online courses in Online Training Center about UML modeling, you can take the free course of sequence diagram at the link below (you simply need to make a free subscription to take the free online courses):
https://www.vp-trainingcenter.com/summary/usingseqcommdiagram.html

I hope all these can answer your question and provide more information about sequence diagram. If you have any further inquiry, please feel free to ask.

Best regards,
Lilian Wong[/quote]
Hi Lilian,

I have already looked at the resources you provided (actually, the link to the UML specs is dead). What I want, is an example of a context in which you would use a send message, so that I would be able to differentiate it from a call message (and similarly for the others).

Regards,
George

Hi George,

Thanks for replying. I’m sorry that I do not have sample project which used types of sequence message.

I checked with our engineers that send message and call message are introduced since UML 1.0, in current UML version, call message no longer exists as a type of message. But we keep the type “Call” for backward compatibility.
Call message is similar to send message, but it is more useful when you want to specify an operation of the classifier’s of the called lifeline.

Best regards,
Lilian Wong

Hi George,

I would like to refine to correct that link for UML 2.2 Specification should be:
http://www.omg.org/spec/UML/2.2/Superstructure/PDF/

Best regards,
Lilian Wong

[quote=LilianWong]Hi George,

I would like to refine to correct that link for UML 2.2 Specification should be:
http://www.omg.org/spec/UML/2.2/Superstructure/PDF/

Best regards,
Lilian Wong[/quote]

Hi Lilian,

I checked the resources website you provided and found the following definitions:

Call Message:
Call message is a kind of message that represents an invocation of operation of target lifeline.

Send Message:
Send message is a kind of message that represents the start of execution.

Sequence Message:
Sequence message is a kind of message that represents the need of performing actions in sequence.

Uninterpreted Message:
Uninterpreted message is a kind of message that represents an uninterpreted call.

I am totally confused - do you mean that with a call message execution does not need to start immediately, but a send message will force execution to begin immediately? But surely this distinction is done at the level of synchronous vs asynchronous?

What would a sequence message specify - a sequence of method calls? Why not use different messages?

What about the uninterpreted messages? How would the sender know that its message was not been interpreted?

All these definitions come from Visual Paradigm Resources page (http://www.visual-paradigm.com/VPGallery/diagrams/Sequence.html) and as you provide them I thought it sensible to ask what are the differences. Surely, there exist as otherwise you would not have been providing different types (my students keep asking these questions and I know for a fact that many of them are reluctant of using Visual Paradigm at work because they can not understand the differences between all these types)?

Regards,
George

George,

you can check this site:

http://www.uml-diagrams.org/sequence-diagrams.html#message