INFO210_HW2_solution

If so give an example from real life and draw a

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Unformatted text preview: the Cartesian product, |B x G|. (c) Consider the binary relationship set siblings, which models the customary sibling relationship in a family, relating two entities from the entity set Person. Draw and ER diagram of this relationship set. What are the connectivity and cardinality of this relationship set? What key and participation constraints hold? Solution: The relationship set is depicted below. No key constraints hold, because a person may have 0, 1 or several siblings. No participation constraints hold, because not all people have siblings. ssn' name' dob' PERSON' sibling_of' (d) Do there exist instances of one- to- one binary relationship sets in which no total participation constraints hold? If so – give an example from real life and draw a diagram. If not – explain why not. Solution: Yes, a one- to- one binary relationship sets may or may not involve total participation. For example, consider the binary relationship set currently_married that relates entities from entity sets Women and Men. This is a one- to- one binary relationship set in which no total participation constraints hold, assuming that anyone who is currently married is married to exactly one person, and that not everyone is currently married. ssn$ name$ dob$ MAN$ date$ currently_married$ ssn$ name$ dob$ WOMAN$ (e) Do there exist instances of one- to- one binary relationship sets in which no key constraints hold? If so – give an example from real life and draw a diagram. If not – explain why not. Solution: Key constraints hold in all one- to- one binary relationships. This is by definition of a one- to- one relatio...
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