Good evening, I have a question about the second part of the project when it comes to resolving relationships between a "mandatory participation on one Side of a 1:1 relationship" scenario. In the lecture for Week 7, it's stated that "entity with optional participation in relationship is designated as parent entity and entity with mandatory participation is designated as child entity". An example is given involving a client stating a preference, with the preference being optional, so I would assume the preference would be the parent entity. However, in the lecture the example posts a copy of the primary key from the client into the preference, implying the preference is actually the child, not the parent (please refer to the screenshot attached). I also took a look at the textbook and it's the exact same (see the second attached screenshot), it states that the optional participation side should be the parent, yet it designates it as the child instead. What's going on? Additionally, for the first part of the lecture where the one to many (1:*) relationships are resolved, there are no contradictions and it follows the rule that the "many side" is the side where the "*" cardinality appears. Again, this is contradictory to the part about resolving a 1:1 relationship involving mandatory participation on one side, as this part of the lecture implies that the "side" that is optional is opposite to where the side the "0:1" lies (because on the preference side, there's 0:1, and on the client side there's 1:1, however client is designated as the parent rather than the preference, so what does "side" even mean?) Thank you for your time

Here are the screenshots mentioned.

I think these two pictures you provided describe the same concept regarding a 1:1 relationship with mandatory participation on one side. Client is designated as the parent (since every client exists, even if they don't have a preference).Preference is designated as the child (since a preference can only exist if tied to a client).