Hello everyone
i have recently learned activity diagram , and that’s my Home Work it’s about constructing an activity diagram for login and register in a website
I am not sure about the way i used object node !? , also i want to know the difference between object node and object flow ?
http://img28.imageshack.us/img28/6268/loginregsiter.jpg
thanks in advance 
My understanding of object nodes in activity diagrams is that they represent an instantiation of an object that the flow refers to. In your diagram, you have object nodes for E-mail, FirstName, LastName, and Password – do you have classes for each of these? To me, it would make more sense to have a User class with these attributes. That way, your Enter Register Data and Enter Login Data activities will refer to a single User instance.
The flow would look something like this:
Enter Register Data -> User -> Check Availability …
Enter Login Data -> User -> Check Data …
If you really want to refer to multiple object instances simultaneously, I suppose using fork nodes is fine. Currently, your diagram’s flow abruptly stocks are your object nodes, which, to me, makes it a bit difficult to follow.
