Understanding Enhanced Entity-Relationship Generalization Hierarchy PrinciplesEntity relationship many to...
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Understanding Enhanced Entity-Relationship Generalization Hierarchy Principles
Entity relationship many to manyER Diagram translation to tablesEntity Relationship Model - double one to manyCan an entity in an entity-relationship diagram have more than one relationship?Hierarchical permissions in a table stored hierarchyEntity-Relationship Diagrams: Identifying which way a relationship flowsOrganizing a comments table: How to justify the choice?How to express a “some of which are” and “not all are” relationship with enhanced entity-relationship diagrams?Entity-Relationship Diagram Software
I was given this exercise:
(T/F and justify)
It can be said that an entity related to another entity through a
generalization hierarchy:
a) will always have a total participation with respect to the "parent"
b) will always inherit the relationships of the "parent"
My current considerations
Well, I think a) is true because it must be related to the other entity (that's the meaning of "total participation").
I have no idea about b).
I do not understand such a question. Can you clear my mind?
database-design erd
edited Sep 5 '17 at 19:41
MDCCL
6,84331745
asked Aug 23 '17 at 13:27
JustToKnowJustToKnow
11
bumped to the homepage by Community♦ 16 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
add a comment |
I was given this exercise:
(T/F and justify)
It can be said that an entity related to another entity through a
generalization hierarchy:
a) will always have a total participation with respect to the "parent"
b) will always inherit the relationships of the "parent"
My current considerations
Well, I think a) is true because it must be related to the other entity (that's the meaning of "total participation").
I have no idea about b).
I do not understand such a question. Can you clear my mind?
database-design erd
edited Sep 5 '17 at 19:41
MDCCL
6,84331745
asked Aug 23 '17 at 13:27
JustToKnowJustToKnow
11
bumped to the homepage by Community♦ 16 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
add a comment |
I was given this exercise:
(T/F and justify)
It can be said that an entity related to another entity through a
generalization hierarchy:
a) will always have a total participation with respect to the "parent"
b) will always inherit the relationships of the "parent"
My current considerations
Well, I think a) is true because it must be related to the other entity (that's the meaning of "total participation").
I have no idea about b).
I do not understand such a question. Can you clear my mind?
database-design erd
edited Sep 5 '17 at 19:41
MDCCL
6,84331745
asked Aug 23 '17 at 13:27
JustToKnowJustToKnow
11
I was given this exercise:
(T/F and justify)
It can be said that an entity related to another entity through a
generalization hierarchy:
a) will always have a total participation with respect to the "parent"
b) will always inherit the relationships of the "parent"
My current considerations
Well, I think a) is true because it must be related to the other entity (that's the meaning of "total participation").
I have no idea about b).
I do not understand such a question. Can you clear my mind?
database-design erd
database-design erd
edited Sep 5 '17 at 19:41
MDCCL
6,84331745
asked Aug 23 '17 at 13:27
JustToKnowJustToKnow
11
edited Sep 5 '17 at 19:41
MDCCL
6,84331745
asked Aug 23 '17 at 13:27
JustToKnowJustToKnow
11
edited Sep 5 '17 at 19:41
MDCCL
6,84331745
edited Sep 5 '17 at 19:41
MDCCL
6,84331745
edited Sep 5 '17 at 19:41
MDCCL
6,84331745
6,84331745
asked Aug 23 '17 at 13:27
JustToKnowJustToKnow
11
asked Aug 23 '17 at 13:27
JustToKnowJustToKnow
11
asked Aug 23 '17 at 13:27
JustToKnowJustToKnow
11
11
bumped to the homepage by Community♦ 16 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
bumped to the homepage by Community♦ 16 mins ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
According to this page:
A generalization hierarchy is a structured grouping of entities that
share common attributes.
In the example in the article, they use a Person as the generalized entity, and derive Faculty, Staff and Student from the Person.
There are also rules that govern a generalized entity:
- Each instance of the supertype entity must appear in at least one
subtype
- an instance of the subtype must appear in the supertype
- a subtype can not be related to more than one supertype
- generalization hierarchies may be nested by having the subtype of one
hierarchy be the supertype for another
From this, I deduce that the answer must be True, based on the fourth "rule".
answered Aug 23 '17 at 20:40
Randolph WestRandolph West
2,649215
1
Thank you for replying! Have you got any idea about b) ?
– JustToKnow
Aug 23 '17 at 22:31
As I said, I think the answer is true for both statements. I’ve never personally heard of generalized entities.
– Randolph West
Aug 24 '17 at 0:06
1
Ohh, it is okay! Can i ask you something? Have you got any idea if THE entity cant have own defined relations? Can this entity be weak with respect to another entity, that is different from the parent?
– JustToKnow
Aug 24 '17 at 1:14
I mean, following the statement: It can be said that an entity related to another entity through a generalization hierarchy: -cannot have own defined relations -Can this entity be weak with respect to another entity, that is different from the parent? This is really complicated :(
– JustToKnow
Aug 24 '17 at 1:23
add a comment |
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1 Answer
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According to this page:
A generalization hierarchy is a structured grouping of entities that
share common attributes.
In the example in the article, they use a Person as the generalized entity, and derive Faculty, Staff and Student from the Person.
There are also rules that govern a generalized entity:
- Each instance of the supertype entity must appear in at least one
subtype
- an instance of the subtype must appear in the supertype
- a subtype can not be related to more than one supertype
- generalization hierarchies may be nested by having the subtype of one
hierarchy be the supertype for another
From this, I deduce that the answer must be True, based on the fourth "rule".
answered Aug 23 '17 at 20:40
Randolph WestRandolph West
2,649215
1
Thank you for replying! Have you got any idea about b) ?
– JustToKnow
Aug 23 '17 at 22:31
As I said, I think the answer is true for both statements. I’ve never personally heard of generalized entities.
– Randolph West
Aug 24 '17 at 0:06
1
Ohh, it is okay! Can i ask you something? Have you got any idea if THE entity cant have own defined relations? Can this entity be weak with respect to another entity, that is different from the parent?
– JustToKnow
Aug 24 '17 at 1:14
I mean, following the statement: It can be said that an entity related to another entity through a generalization hierarchy: -cannot have own defined relations -Can this entity be weak with respect to another entity, that is different from the parent? This is really complicated :(
– JustToKnow
Aug 24 '17 at 1:23
add a comment |
According to this page:
A generalization hierarchy is a structured grouping of entities that
share common attributes.
In the example in the article, they use a Person as the generalized entity, and derive Faculty, Staff and Student from the Person.
There are also rules that govern a generalized entity:
- Each instance of the supertype entity must appear in at least one
subtype
- an instance of the subtype must appear in the supertype
- a subtype can not be related to more than one supertype
- generalization hierarchies may be nested by having the subtype of one
hierarchy be the supertype for another
From this, I deduce that the answer must be True, based on the fourth "rule".
answered Aug 23 '17 at 20:40
Randolph WestRandolph West
2,649215
1
Thank you for replying! Have you got any idea about b) ?
– JustToKnow
Aug 23 '17 at 22:31
As I said, I think the answer is true for both statements. I’ve never personally heard of generalized entities.
– Randolph West
Aug 24 '17 at 0:06
1
Ohh, it is okay! Can i ask you something? Have you got any idea if THE entity cant have own defined relations? Can this entity be weak with respect to another entity, that is different from the parent?
– JustToKnow
Aug 24 '17 at 1:14
I mean, following the statement: It can be said that an entity related to another entity through a generalization hierarchy: -cannot have own defined relations -Can this entity be weak with respect to another entity, that is different from the parent? This is really complicated :(
– JustToKnow
Aug 24 '17 at 1:23
add a comment |
According to this page:
A generalization hierarchy is a structured grouping of entities that
share common attributes.
In the example in the article, they use a Person as the generalized entity, and derive Faculty, Staff and Student from the Person.
There are also rules that govern a generalized entity:
- Each instance of the supertype entity must appear in at least one
subtype
- an instance of the subtype must appear in the supertype
- a subtype can not be related to more than one supertype
- generalization hierarchies may be nested by having the subtype of one
hierarchy be the supertype for another
From this, I deduce that the answer must be True, based on the fourth "rule".
answered Aug 23 '17 at 20:40
Randolph WestRandolph West
2,649215
According to this page:
A generalization hierarchy is a structured grouping of entities that
share common attributes.
In the example in the article, they use a Person as the generalized entity, and derive Faculty, Staff and Student from the Person.
There are also rules that govern a generalized entity:
- Each instance of the supertype entity must appear in at least one
subtype
- an instance of the subtype must appear in the supertype
- a subtype can not be related to more than one supertype
- generalization hierarchies may be nested by having the subtype of one
hierarchy be the supertype for another
From this, I deduce that the answer must be True, based on the fourth "rule".
answered Aug 23 '17 at 20:40
Randolph WestRandolph West
2,649215
answered Aug 23 '17 at 20:40
Randolph WestRandolph West
2,649215
answered Aug 23 '17 at 20:40
Randolph WestRandolph West
2,649215
answered Aug 23 '17 at 20:40
Randolph WestRandolph West
2,649215
2,649215
1
Thank you for replying! Have you got any idea about b) ?
– JustToKnow
Aug 23 '17 at 22:31
As I said, I think the answer is true for both statements. I’ve never personally heard of generalized entities.
– Randolph West
Aug 24 '17 at 0:06
1
Ohh, it is okay! Can i ask you something? Have you got any idea if THE entity cant have own defined relations? Can this entity be weak with respect to another entity, that is different from the parent?
– JustToKnow
Aug 24 '17 at 1:14
I mean, following the statement: It can be said that an entity related to another entity through a generalization hierarchy: -cannot have own defined relations -Can this entity be weak with respect to another entity, that is different from the parent? This is really complicated :(
– JustToKnow
Aug 24 '17 at 1:23
add a comment |
1
Thank you for replying! Have you got any idea about b) ?
– JustToKnow
Aug 23 '17 at 22:31
As I said, I think the answer is true for both statements. I’ve never personally heard of generalized entities.
– Randolph West
Aug 24 '17 at 0:06
1
Ohh, it is okay! Can i ask you something? Have you got any idea if THE entity cant have own defined relations? Can this entity be weak with respect to another entity, that is different from the parent?
– JustToKnow
Aug 24 '17 at 1:14
I mean, following the statement: It can be said that an entity related to another entity through a generalization hierarchy: -cannot have own defined relations -Can this entity be weak with respect to another entity, that is different from the parent? This is really complicated :(
– JustToKnow
Aug 24 '17 at 1:23
1
1
Thank you for replying! Have you got any idea about b) ?
– JustToKnow
Aug 23 '17 at 22:31
Thank you for replying! Have you got any idea about b) ?
– JustToKnow
Aug 23 '17 at 22:31
As I said, I think the answer is true for both statements. I’ve never personally heard of generalized entities.
– Randolph West
Aug 24 '17 at 0:06
As I said, I think the answer is true for both statements. I’ve never personally heard of generalized entities.
– Randolph West
Aug 24 '17 at 0:06
1
1
Ohh, it is okay! Can i ask you something? Have you got any idea if THE entity cant have own defined relations? Can this entity be weak with respect to another entity, that is different from the parent?
– JustToKnow
Aug 24 '17 at 1:14
Ohh, it is okay! Can i ask you something? Have you got any idea if THE entity cant have own defined relations? Can this entity be weak with respect to another entity, that is different from the parent?
– JustToKnow
Aug 24 '17 at 1:14
I mean, following the statement: It can be said that an entity related to another entity through a generalization hierarchy: -cannot have own defined relations -Can this entity be weak with respect to another entity, that is different from the parent? This is really complicated :(
– JustToKnow
Aug 24 '17 at 1:23
I mean, following the statement: It can be said that an entity related to another entity through a generalization hierarchy: -cannot have own defined relations -Can this entity be weak with respect to another entity, that is different from the parent? This is really complicated :(
– JustToKnow
Aug 24 '17 at 1:23
add a comment |
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