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State whether each of the following statements/propositions is True or False.
All databases are relational.
False
There are also hierarchical databases, network databases, object-oriented databases, and databases created without the benefit of a DBMS.
The relational model was first introduced by Ted Codd of IBM Research in a classic paper "A Relational Model of Data for Large Shared Data Banks".
True
A relation is physically represented as a table.
True
{d, i, l, m, o, m} is a set.
False
Each element of a set should appear only once.
{d, i, l, m, o, m} is a bag, or multi-set.
{r, a, t, b, e, r, t} is a bag.
True
{a, b, c} is equal to {b, a, c}.
True
{a, b, c} is equal to {A, B, C}.
False
Case is significant.
The empty set is represented by { } or Ø.
True
The empty set should not be represented by {Ø}.
True
Empty Set (also called the Null Set)
{Ø} is a set which contains the empty set and is therefore not empty.
The proper subsets of {x, y} are {x} and {y}.
False
The proper subsets of {x, y} are {x} and {y} and { }.
The proper subsets of {x, y} are {x} and {y} and Ø.
Complete each of the sentences below.
The length of the line in the sentences is constant and does not necessarily indicate the length of the answer to be supplied.
One organisation which stores information about me on
a database is ANU.
One organisation which stores information about me on
a database is Centrelink.
One organisation which stores information about me on
a database is a bank.
One organisation which stores information about me on
a database is the Federal Police.
One organisation which stores information about me on
a database is the CIA.
The relational model has its theoretical basis in set theory and first-order predicate logic.
The number of attributes in a relation is called its degree.
The number of tuples in a relation is called its cardinality.
Each tuple is distinct; there are no duplicate tuples.
slide 9 from 2005 Lecture 7
The order of tuples has no semantic significance.
slide 9 from 2005 Lecture 7
All information in a relational database is represented explicitly at the logical level and in exactly one way - by values in a table.
slide 13 from 2005 Lecture 8
The totality of objects of interest is called the universal set, which is denoted by U.
The objects in a set are called the elements of the set.
The null set is a subset of
every set.
The empty set is a subset of
every set.
The subsets of S {a, b} are Ø {a} {b}
{a, b}.
The subsets of S {a, b} are { } {a} {b}
{a, b}.
If a set contains 4 elements, the set has 16 subsets.
If a set contains 5 elements, the set has 31 proper subsets.
If A equals B, then A is a subset of B and B is a subset of A.
The complement of A is the set of all elements x in U such that x is not in A.
The difference of B minus A is the set of all elements x in U such that x is in B and x is not in A.
The intersection of A and B is the set of all elements x in U such that x is in A and x is in B.
The union of A and B is the set of all elements x in U such that x is in A or x is in B.
Complete each of the following truth tables.
| fred | mary | NOT fred | (NOT fred) AND mary |
|---|---|---|---|
| TRUE | TRUE | FALSE | FALSE |
| TRUE | FALSE | FALSE | FALSE |
| FALSE | TRUE | TRUE | TRUE |
| FALSE | FALSE | TRUE | FALSE |
| fred | mary | fred AND mary | NOT (fred AND mary) |
|---|---|---|---|
| TRUE | TRUE | TRUE | FALSE |
| TRUE | FALSE | FALSE | TRUE |
| FALSE | TRUE | FALSE | TRUE |
| FALSE | FALSE | FALSE | TRUE |
| fred | mary | fred OR mary | fred XOR mary |
|---|---|---|---|
| TRUE | TRUE | TRUE | FALSE |
| TRUE | FALSE | TRUE | TRUE |
| FALSE | TRUE | TRUE | TRUE |
| FALSE | FALSE | FALSE | FALSE |
Complete the following truth table.
| fred | mary | NOT fred AND mary |
|---|---|---|
| TRUE | TRUE | |
| TRUE | FALSE | |
| FALSE | TRUE | |
| FALSE | FALSE |
|
URL: http://computer/student/comp2400.2006/tutlabs/tut1/SolnNotes.shtml
Last modified: Sunday, 30-Jul-2006 19:07:26 EST |