Subtypes and Supertypes
A subtype is a subset of another entity.For example,
consider the entity COURSE. There are two types of COURSEs, semester and standalone. The entity, COURSE is the supertype, and SEMESTER and STANDALONE are the subtypes. There are some attributes that are common to both the subtypes, for example: “course code”, “name”, and “content”. STANDALONE courses have some attributes such as “duration” that do not belong to the subtype, SEMESTER. The SEMESTER subtype has some attributes such as “semester_no” that do not belong to the STANDALONE subtype
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