Why do some Entities/Tables have rounded corners while some others have square shaped corners? (4305574)

Question:

Why do some Entities/Tables have rounded corners while some others have square shaped corners?

Solution: 

In figure 1 below the Entity E/14 is rounded because there is an Identifying Relationship (solid line) connected to that Entity and it is the Child of another Entity.  The Entity E/13 is connected by a dotted line (Non Identifying Relationship) so that has square corners.  This means that when a Foreign Key (FK) is also a Primary Key (PK) or even a part of a PK in an Entity, the corners are rounded whereas if the PK of an Entity is not impacted by an FK, the corners stay squared as in a stand alone Entity.