What do these arrows in design pattern diagrams mean?
The arrows mean distinct things. This is a UML (unified modeling language) diagram. Rules for reading and writing these diagrams are pretty well-established, and you should be able to look up some references.

In that diagram, the hollow arrow means generalization (i.e., inheritance, IS_A), and the hollow diamond means aggregation (i.e., a kind of association, HAS_A). The dotted line connects a comment/label and contains auxiliary/meta information (I believe, but double check this one).