For each of the following enterprise constraints decide whether • it is already
ID: 3594234 • Letter: F
Question
For each of the following enterprise constraints decide whether
• it is already expressed in the Enhanced Entity-Relationship model
(EER) of the below diagram
• it is not already expressed in the EER of the below diagram
but could be expressed using only features of an EER model.
• cannot be expressed in the EER of the below diagram using
only features of an EER model.
In each case explain your answer briefly but clearly.
(a) A table order originates from exactly one table of one restaurant.
(b) Two table orders dispatched at (roughly) the same time must
originate from different tables.
Receives by phone Restaurant name phone_line phone num Contalns dateTime billingNo total Order Originates_from Table foptional,orh number PhoneOrder street waiter deliveryAddress postcode cityExplanation / Answer
(a) A table order originates from exactly one table of one restaurant.
It is already expressed in the Enhanced Entity-Relationship model diagram. Because in the diagram TableOrder and Table having M:1 relationship which means Many table orders originates from One table only. And Table and Restaurent having M:1 relationship which means many tables will be there in one Restaurent and One restaurent contains many Tables. Which means Table order originates from only one table which is of One restaurent only.
b) Two table orders dispatched at (roughly) the same time must originate from different tables.
it is not already expressed in the EER of the below diagram but could be expressed using only features of an EER model. Here we are having M:1 relationship between TableOrder and Table. So the given condition is not satisfied as More table orders will be originated from one and only one table ,here it is given two orders originated fom multiple tables. Inorder to satisfy this condition we must specify relationship as M:N between TableOrder and Table.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.