Which UML diagram is the best for showing dependency between our IT system and other external IT systems?
For example I would like to show on diagram:
system A gets data from system B
system B can call some functionality from system A
I’m wondering between component diagram and sequence diagram.
What do you think?
How about communication diagram? Like sequence diagram, communication diagram is also for visualizing the interaction between objects. What makes communication diagram different is that it focuses on the existence of relationship between objects, rather than the sequence of calls. In other words, with a communication diagram you can know easily which object has a relationship with another object.
Hope this helps.