ER図に外部キーを含めるかどうか
多重度を加味して書いたときって、互いのことって属性として記述しないの？
https://gyazo.com/0f8ef2e5adb67359e4ae8f9673ec947e
この図だったら、配送先の属性として、送り主のような属性は記述しないの？
しないらしい
実際にclassとして実装する時のpropertyはER図より増えるってことか
だとしてもこんな感じで、結ぶ線の上に属性を書くのでは
https://gyazo.com/8ac6574e24acdf05454f881ad790a271
クラス図かER図で異なるのかも知れない
自分できめてok
When including attributes on ER diagrams, you must decide whether to include foreign keys as attributes. This probably depends on how closely you are trying to represent relational table structures. If your diagram is a logical model which is not meant to imply a relational implementation, then it is better to leave these out because the associative relationships already convey the way that entities are associated. For example, a JSON data structure can implement a one-to-many relationship without the need for foreign key properties, using arrays. Similarly an object-oriented programming language may use pointers or references to collections. Even for models that are intended for relational implementation, you might decide that inclusion of foreign key attributes duplicates information already portrayed by the relationships, and does not add meaning to entities. Ultimately, it's your choice. ref