CS 6400 - EXAM 3 LATEST
logical (or conceptual) level - ANSWERS-how users interpret the
relation schemas and the meaning of their attributes
implementation (or physical storage) level - ANSWERS-how the tuples
in a base relation are stored and updated
bottom-up design methodology - ANSWERS-(also called design by
synthesis) considers the basic relationships among individual attributes
as the starting point and uses those to construct relation schemas
top-down design methodology - ANSWERS-(also called design by
analysis) starts with a number of groupings of attributes into relations
that exist together naturally
measures to determine the quality of relation schema design -
ANSWERS-■ Making sure that the semantics of the attributes is clear in
the schema
■ Reducing the redundant information in tuples
■ Reducing the NULL values in tuples
■ Disallowing the possibility of generating spurious tuples
END OF
PAGE
1
, CS 6400 - EXAM 3 LATEST
semantics of a relation - ANSWERS-refers to its meaning resulting from
the interpretation of attribute values in a tuple
update anomalies - ANSWERS-can be classified into insertion
anomalies, deletion anomalies, and modification anomalies
Insertion Anomalies - ANSWERS-occur when users attempt to store an
attribute value in the system but they cannot because the value of
another unnecessary but required attribute is not known
Deletion Anomalies - ANSWERS-occur when a value for one attribute
that users wish to keep is unexpectedly removed when a value for
another attribute is deleted
Modification Anomalies - ANSWERS-occur when changes to multiple
instances of an entity (rows of a table) are needed to effect an update to a
single value of an attribute
Spurious tuples - ANSWERS-Tuples generated by joining two relations
on attributes that are not keys or foreign keys on these relations.
END OF
PAGE
2
, CS 6400 - EXAM 3 LATEST
Waste of storage space - ANSWERS-due to NULLs and the difficulty of
performing selections, aggregation operations, and joins due to NULL
values
A functional dependency (A->B) - ANSWERS-occurs when the
attribute A uniquely determines B. A = left-hand side, B=right-hand-
side.
-is a property of the semantics or meaning of the attributes.
FD or f.d. - ANSWERS-abbreviation for functional dependency
Candidate Key - ANSWERS-An attribute, or combination of attributes,
that uniquely identifies a row in a relation.
legal relation states (or legal extensions) of R - ANSWERS-Relation
extensions r(R) that satisfy the functional dependency constraints
FD cannot be inferred automatically - ANSWERS-must be defined
explicitly by someone who knows the semantics of the attributes of R.
END OF
PAGE
3
, CS 6400 - EXAM 3 LATEST
diagrammatic notation - ANSWERS-isplaying FDs: Each FD is
displayed as a horizontal
Normalization of Data - ANSWERS-a process of analyzing the given
relation schemas based on their FDs and primary keys to achieve the
desirable properties of (1) minimizing redundancy and (2) minimizing
the insertion, deletion, and update anomalies
Boyce-Codd Normal Form (BCNF) - ANSWERS-A special type of third
normal form (3NF) in which every determinant is a candidate key. A
table in BCNF must be in 3NF.
normal form test - ANSWERS-is decomposed into smaller relation
schemas that contain a subset of the attributes and meet the test that was
otherwise not met by the original relation.
nonadditive join - ANSWERS-or lossless join property, guarantees that
the spurious tuple generation problem does not occur
dependency preservation property - ANSWERS-ensures that each
functional dependency is represented in some individual relation
resulting after decomposition
END OF
PAGE
4
logical (or conceptual) level - ANSWERS-how users interpret the
relation schemas and the meaning of their attributes
implementation (or physical storage) level - ANSWERS-how the tuples
in a base relation are stored and updated
bottom-up design methodology - ANSWERS-(also called design by
synthesis) considers the basic relationships among individual attributes
as the starting point and uses those to construct relation schemas
top-down design methodology - ANSWERS-(also called design by
analysis) starts with a number of groupings of attributes into relations
that exist together naturally
measures to determine the quality of relation schema design -
ANSWERS-■ Making sure that the semantics of the attributes is clear in
the schema
■ Reducing the redundant information in tuples
■ Reducing the NULL values in tuples
■ Disallowing the possibility of generating spurious tuples
END OF
PAGE
1
, CS 6400 - EXAM 3 LATEST
semantics of a relation - ANSWERS-refers to its meaning resulting from
the interpretation of attribute values in a tuple
update anomalies - ANSWERS-can be classified into insertion
anomalies, deletion anomalies, and modification anomalies
Insertion Anomalies - ANSWERS-occur when users attempt to store an
attribute value in the system but they cannot because the value of
another unnecessary but required attribute is not known
Deletion Anomalies - ANSWERS-occur when a value for one attribute
that users wish to keep is unexpectedly removed when a value for
another attribute is deleted
Modification Anomalies - ANSWERS-occur when changes to multiple
instances of an entity (rows of a table) are needed to effect an update to a
single value of an attribute
Spurious tuples - ANSWERS-Tuples generated by joining two relations
on attributes that are not keys or foreign keys on these relations.
END OF
PAGE
2
, CS 6400 - EXAM 3 LATEST
Waste of storage space - ANSWERS-due to NULLs and the difficulty of
performing selections, aggregation operations, and joins due to NULL
values
A functional dependency (A->B) - ANSWERS-occurs when the
attribute A uniquely determines B. A = left-hand side, B=right-hand-
side.
-is a property of the semantics or meaning of the attributes.
FD or f.d. - ANSWERS-abbreviation for functional dependency
Candidate Key - ANSWERS-An attribute, or combination of attributes,
that uniquely identifies a row in a relation.
legal relation states (or legal extensions) of R - ANSWERS-Relation
extensions r(R) that satisfy the functional dependency constraints
FD cannot be inferred automatically - ANSWERS-must be defined
explicitly by someone who knows the semantics of the attributes of R.
END OF
PAGE
3
, CS 6400 - EXAM 3 LATEST
diagrammatic notation - ANSWERS-isplaying FDs: Each FD is
displayed as a horizontal
Normalization of Data - ANSWERS-a process of analyzing the given
relation schemas based on their FDs and primary keys to achieve the
desirable properties of (1) minimizing redundancy and (2) minimizing
the insertion, deletion, and update anomalies
Boyce-Codd Normal Form (BCNF) - ANSWERS-A special type of third
normal form (3NF) in which every determinant is a candidate key. A
table in BCNF must be in 3NF.
normal form test - ANSWERS-is decomposed into smaller relation
schemas that contain a subset of the attributes and meet the test that was
otherwise not met by the original relation.
nonadditive join - ANSWERS-or lossless join property, guarantees that
the spurious tuple generation problem does not occur
dependency preservation property - ANSWERS-ensures that each
functional dependency is represented in some individual relation
resulting after decomposition
END OF
PAGE
4
