Understanding the reasons why the arrow points the arrow in the opposite direction

Question

In class diagrams, I usually see something like ClassA that extends ClassB, where the arrow points to ClassA. An example is here http://bit.ly/GFakDu . It always confused me. Why doesn't the arrow point to ClassB?

Answer 1

UML is simply misused in these diagrams. The arrowhead should be a triangle (and not open), it should point to a different direction, and it is called the implementation of not a gun. Therefore, if I did not completely interpret the diagrams incorrectly, the author (of the diagrams or the software they created) simply did not know how to use UML correctly.

In this diagram (just found using Google) you can see the correct visualization of the "SearchService" class that implements the "SiteSearch" interface.

In the following diagram, several classes are generalized (specialize, expand) the class "Account".

In this site you can get a review (it looks right at first glance). If you want to be sure that you should study the specification (find a pdf file there).

Answer 2

I think the confusion here is due to differences in how people relate to the intricacies of English grammar.

Some people may be inclined to complete the “inconvenient”, but the UML standard token will “expand” as “expand”, while others will fill it as “advanced” when viewing or developing a chart. Hence the differences in interpretation.