Ugly ER notation

Started day with reading Garcia, Ulman's and Widom book:
"Database Systems: The Complete Book" (2nd ed, Russian translation)

First of all looked through all, and found it very interesting in the details that met my eyes.

Also it has a very good descriptions of terminology generally used.

However the second chapter, passed is ugliest one. I haven't seen application that use notation proposed for years.

Week entities, round and common arrows, rhombuses, in what database applications they are used?
And a lot of "philosophy" there, that is description of a lot of correct and incorrect ways to present data in the model. And the 3rd chapter begins with statement that relational model is different from previous presented.

Ok, it seems that 2nd chapter could be passed without given a lot of attention to.

Resource related to the book:

http://infolab.stanford.edu/~ullman/fcdb/aut07/index.html#lecture

going to play a little with examples from there.