UML sequence Diagram

[saurav sarkar]

Hi All,

I have a general question in Sequence diagrams.
Can i have two objects with same name in a single sequence
diagram.
The Problem is i need to depict the full flow of my app.
So it encounters the same class in the beginning of the flow
and also in the end part of the flow.
I know i break it and have a reference of the diagrams.
But is it allowed in UML to put the same class twice
in the single sequence diagram.

EA perfectly allows that in UML2.0 specification.
Please advise.

Thanks in advance
Saurav

[Gabriel Claramunt]

You can have many objects of the same class in a sequence diagram.
You shouldn't be able to to have different objects with the same name, I'm not sure if the UML specification allows it, but it will be very confusing!
Supose you have o1 of class C1 and o2 of class C2

Instead of

o1:C1    o2:C2
  |        |
  |------->|
  |        |
  |<-------|

<br /> <br /> <br /> you'll have:<br />

o1:C1    o2:C2    o1:C1
  |        |        |
  |------->|        |
  |        |------->|

In the first diagram o1 send a message to o2 and o2 sends a message back.
In the second diagram, to what object o2 is sending the message? if the first and last objects are the same, why it appears twice? if they're different, why they have the same name?
Maybe there's a special occation in which can be useful, but I can't think any example...