'Entity diagram questions using the same entity at different timing
Hi I have an questions and about a bus transport system modelled into E-R diagram. I am confused about a part where a a person needs to tap card IN and OUT of the bus when boarding and alighting respectively and data for time of boarding and alighting needs to be recorded. So the entities that i have right now is the person and the physical bus(identified by the bus plate) and a bus-stop as a strong entity but i am unsure how to link them.
From my understanding..
I cannot use ternary relationship connecting all three entity as there are more than bus stop and ternary entity will only account for a person, a bus and a busstop.
So is it possible to do a unary relationship for busstop which at the same time connects to the a person (forming associative entity) so we know the person and his start and his destination?
Sources
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