In most cases, it will only clutter up your diagrams. Login is neither complex (*) nor does it give you much added value as a use case. In your textual document that includes the use cases with description, include as a prerequisite a list of features that require a successful login. Easier to track and … Read more
This shows navigability. A can see (means it has an attribute referencing) B. In contrast B has no idea about/reference to A. As @JimL commented, your arrow is wrong and only used for stereotype definition. I’m referring to the unfilled arrow which indicates navigability of associations from which I assume you actually meant that. UML … Read more
Some context: Recently for graduate school I researched UML tools for usability and UML comprehension in general for an independent project. I also model/architect for a living. The previous posts have too many answers and not enough questions. A common misunderstanding is that UML is about creating diagrams. Sure, diagrams are important, but really you … Read more
If else condition, also called alternatives in UML terms can indeed be represented in sequence diagrams. Here is a link where you can find some nice resources on the subject http://www.ibm.com/developerworks/rational/library/3101.html
An association almost always implies that one object has the other object as a field/property/attribute (terminology differs). A dependency typically (but not always) implies that an object accepts another object as a method parameter, instantiates, or uses another object. A dependency is very much implied by an association.
Maybe this can help you, but i don’t think you will find the perfect explanation: The difference is one of implication. Aggregation denotes whole/part relationships whereas associations do not. However, there is not likely to be much difference in the way that the two relationships are implemented. That is, it would be very difficult to … Read more
Extend is used when a use case adds steps to another first-class use case. For example, imagine “Withdraw Cash” is a use case of an Automated Teller Machine (ATM). “Assess Fee” would extend Withdraw Cash and describe the conditional “extension point” that is instantiated when the ATM user doesn’t bank at the ATM’s owning institution. … Read more