Difference between Sequence & Communication Diagram (UML)

Question

What is the difference between sequence diagrams and communication (collaboration) diagrams in UML?

Solution 1

Quoting Wikipedia:

Communication diagrams show a lot of the same information as sequence diagrams, but because of how the information is presented, some of it is easier to find in one diagram than the other. Communication diagrams show which elements each one interacts with better, but sequence diagrams show the order in which the interactions take place more clearly.

In essence, collaboration diagram emphasizes on which objects interacts with each other while sequence diagrams put more emphasis on the actual order. But they are actually equivalent, in exception to a little more details visible in sequence diagrams, like when and by whom the object was created/destroyed.

Solution 2

Sequence diagram make it easier to follow the interactions since they are done from top to bottom, so finding message ordering is pretty simple. But if you have many object interacting, the diagram becomes hard to read.

Communication diagrams display what messages are passed between the objects with the sequence written on top of the message. For large amounts of objects, it is easier to understand than the sequence diagram, but message sequencing is harder to understand.