Answer the following questions about the given statement: ∀t : Trainers • ∃c : Course • (t,c) ∈Teaches ∧c.time = 2 •What does this statement mean? •Is this statement a set or a predicate? •What does the statement evaluate to based on the current system state?

Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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Answer the following questions about the given statement:

∀t : Trainers • ∃c : Course • (t,c) ∈Teaches ∧c.time = 2

•What does this statement mean?
•Is this statement a set or a predicate?
•What does the statement evaluate to based on the current system state?

 



Examples for reference:
•∃g : Owner • g.name = gymowner ∧g.email = test
-There exists an owner with the name gymowner and email test
-predicate
-false

•{c : Course |∃co : Customer • (co,c) ∈Books}
-Set of all Courses which are booked by a customer
-set
-{Boxing,WeightLifting,Yoga1,Wrestling}

•{t : Trainer |#{c : Course |(t,c) ∈Teaches}>1}
-Set of all Trainers who teach more than 1 class.
-set
-{Trainer 2}

Teaches association between Owner/Teacher and Course
Gym Owner: Owner
name = GymOwner
email = gymowner@gym.com
password=gymowner
Trainer 1: Trainer
name Trainer1
email trainer1@gym.com
password = trainer1
credit - 3
Trainer 2: Trainer
name Trainer2
email trainer2@gym.com
password = trainer2
credit = 2
Wrestling : Course
time = 2
type = Wrestling
id = 1
private=false
Boxing: Course
time = 2
type = Boxing
id = 2
private = false
Weightlifting Course
time = 2
type
id=3
private = false
Weightlifting
Yogal: Course
time = 3
type = Yoga
id = 4
private = true
Yoga2: Course
time = 4
type = Yoga
id = 5
private = false
Customer 1: Customer
name Customer1
email= customer1@gym.com
password
customer1
classcredit
class credit - 0
Customer 2: Customer
name Customer2
email customer2@gym.com
password = customer2
classcredit
class credit = 1
Customer 3: Customer
name Customer3
email customer3@gym.com
password customer
classcredit
class credit = 4
Customer 4: Customer
name Customer4
email = customer4@gym.com
password = customer4
classcredit
class credit = 5
Customer 5: Customer
name Customer5
email customer5@gym.com
password customer5
classcredit
class credit 1
Customer 6: Customer
name Customer6
email customer6@gym.com
customer6
password
classcredit
class credit = 10
Customer 7: Customer
name Customer7
email customer7@gym.com
customer7
password
classcredit
class credit = 2
Books association between Course and Customer
Transcribed Image Text:Teaches association between Owner/Teacher and Course Gym Owner: Owner name = GymOwner email = gymowner@gym.com password=gymowner Trainer 1: Trainer name Trainer1 email trainer1@gym.com password = trainer1 credit - 3 Trainer 2: Trainer name Trainer2 email trainer2@gym.com password = trainer2 credit = 2 Wrestling : Course time = 2 type = Wrestling id = 1 private=false Boxing: Course time = 2 type = Boxing id = 2 private = false Weightlifting Course time = 2 type id=3 private = false Weightlifting Yogal: Course time = 3 type = Yoga id = 4 private = true Yoga2: Course time = 4 type = Yoga id = 5 private = false Customer 1: Customer name Customer1 email= customer1@gym.com password customer1 classcredit class credit - 0 Customer 2: Customer name Customer2 email customer2@gym.com password = customer2 classcredit class credit = 1 Customer 3: Customer name Customer3 email customer3@gym.com password customer classcredit class credit = 4 Customer 4: Customer name Customer4 email = customer4@gym.com password = customer4 classcredit class credit = 5 Customer 5: Customer name Customer5 email customer5@gym.com password customer5 classcredit class credit 1 Customer 6: Customer name Customer6 email customer6@gym.com customer6 password classcredit class credit = 10 Customer 7: Customer name Customer7 email customer7@gym.com customer7 password classcredit class credit = 2 Books association between Course and Customer
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