I was just looking at the sequence diagrams in Cade's 'SCEA for Java EE study guide'. In the sequence diagrams he has used the open headed arrow rather than the filled triangle.
This means all the messages are asychronous???
posted 6 years ago
It may have been dependent on the tool used to create the diagrams. Dont worry about that. If your design has synchronous messages, then indicate it using the appropriate arrows. Same goes for asynchronous. The rectangular bar on the object's lifeline will change accordingly. Thats the most important visual indicator. I think thats all that matters.