Finally, if Registration and AppDashBoard are UI elements, it would be helpful to distinguish them from other elements that are not visible to the user.In your case this is a minor issue, since we can easily find out that it should be the account database. ) shall cover the lifeline that should react first, as explained here. By the way, a minor issue in your diagram: The interaction constraint that guard operands in an alt fragment (e.g.But otherwise, it's quickly only wishful thinking that has nothing to do with UML semantics. If you have some clear messages that correspond to information content provided to or by the actor, the sequence diagram stays understandable. When you use actors in sequence diagram as explained here, then be at least careful with messages exchanged with the actor. More generally, by the book, actors should in principle not appear in a sequence diagram, even if it's a common practice.Does this mean that your system just tells the user that he/she should go to AppDashBoard ? In fact, does the actor do anything with the message at all: isn't it your system that will display another windows or another page regardless of what the user is doing? You have to avoid this. Login screen sends a message like Redirect to AppDashBoard to the actor.This diagram is unfortunately ambiguous and misleading.

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