sequence diagram activation level

[sieme]

Hello,

Does anybody know why sometimes the 'raise/lower activation level' option isn't available in the context menu?, sometimes I need the option, and it isn't there...

Also; when 1 draw a synchronous message arrow from a source lifeline that is raised 3 levels, then why does the activation level of the source is lowered 3 levels? (subsequent to the point of exit of the source of the message). Note that this doesn't always happen; what is the logic/cause?

Note that I have above problems in the context of sending a synchronous message from A to B where within the context of B synchronous calls are made back to A, before the return (dotted line) of the original call from A to B is made. I used to have it all depicted correctly until I added some calls above this sequence and then Enterprise changed the activation levels below it and I can't get it back the way it was..

[sieme]

I still don't understand but it seems the ending of the 3 level activation seems to have something to do with a preceding raising and lowering of the activity level.

Some messages before on the same lifeline I introduced a raising of the activity level with some messages sourcing from that level. Then subsequently I lowered the activation using a return message ('is return' checked). If I remove that return message enterprise decides that the lowering of the levels I described (which is some number of messages lower on the same life line) isn't applicable any more.