Hi Friends,

Can any one tell me how to show threads in Sequence diagrams.

Well,
There are of course several ways to show threads in sequence diagrams.
Usually I start modelling threads (or thread of control) with one composite (structured) class that controls and maintain all thread specific attributes (such as thread prio, sched policy, affinity, name etc). This "Thread Boundary class" defines also the refined software architecture in its inner structure where all contained parts executes within the thread context of the Thread Boundary class. If you then add a sterotype ,i.e <THREAD_A>, to the Thread Container class this will show up nicely in the sequence diagram.

One example of how to model the actual parallel execution is shown in Figure 17 in http://www.ibm.com/developerworks/ratio ... /3101.html.
In short:
1. Model one execution block, within the object of the same thread, with one interaction operator
2. Set the type of of this interaction operator to "parllell" (you can also define a "PARALLEL" sterotype for these types interaction operators")
3. Add execution occurances
4. Add operand seperators for the different parallel activities

Best Regards//
LGJ

"the refined software architecture in its inner structure where all contained parts executes within the thread context of the Thread Boundary class"

Slight deviation from the purpose of the thread but you should be aware that there was a long-standing issue with Rhapsody where this only applied to the 'first level' reactive parts in a composite class. Reactive parts within parts were erroneously using the main thread (default) as their active context. I'm using 7.5.1.1 where the problem is now fixed (a class dependent setActiveContext is now generated for each reactive class). I know the problem still existed as recently as 7.4 but I'm not sure when it got fixed.

Back to the main subject. Colour your execution occurances per thread.