INF2603 assignment 2 semester 2 2020 solutions
QUESTION 1
a. What does it mean to say that a database displays both entity integrity and referential
integrity? (2)
Entity integrity describes a condition in which all tuples with a table are uniquely identified by
their primary key. The unique value requirement prohibits a null primary key value, because
nulls are not unique. Referential integrity describes a condition i which a foreign key value has a
match i the corresponding table or in which the foreign key value is null. The null foreign key
value makes it possible not to have a corresponding, but the matching requirement on values that
are not null make it impossible to have an invalid value.
b. What is a strong (or identifying) relationship, and how is it depicted in a Crow’s Foot
ERD? (2)
A strong relationship exists when en entity is existence-dependent on another entity and inherits
at least part of its primary key from that entity. The Visio Professional software shows the
strong relationship as a solid line. In other words, a strong relationship exists when a weak entity
is related to its parent entity
c. What is Hadoop? (2)
Hadoop is a Java-based, open-source, high-speed, fault-tolerant distributed storage and
computational framework. Hadoop uses low-cost hardware to create clusters of thousands of
computer nodes to store and process data. Hadoop originated from Google‟s work on distributed
file systems and parallel processing and is currently supported by the Apache Software
Foundation. Hadoop has several modules, but the two main components are Hadoop Distributed
File System (HDFS) and MapReduce.
d. How would you (graphically) identify each of the following ERM components in a
Crow’s Foot model? (8)
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QUESTION 1
a. What does it mean to say that a database displays both entity integrity and referential
integrity? (2)
Entity integrity describes a condition in which all tuples with a table are uniquely identified by
their primary key. The unique value requirement prohibits a null primary key value, because
nulls are not unique. Referential integrity describes a condition i which a foreign key value has a
match i the corresponding table or in which the foreign key value is null. The null foreign key
value makes it possible not to have a corresponding, but the matching requirement on values that
are not null make it impossible to have an invalid value.
b. What is a strong (or identifying) relationship, and how is it depicted in a Crow’s Foot
ERD? (2)
A strong relationship exists when en entity is existence-dependent on another entity and inherits
at least part of its primary key from that entity. The Visio Professional software shows the
strong relationship as a solid line. In other words, a strong relationship exists when a weak entity
is related to its parent entity
c. What is Hadoop? (2)
Hadoop is a Java-based, open-source, high-speed, fault-tolerant distributed storage and
computational framework. Hadoop uses low-cost hardware to create clusters of thousands of
computer nodes to store and process data. Hadoop originated from Google‟s work on distributed
file systems and parallel processing and is currently supported by the Apache Software
Foundation. Hadoop has several modules, but the two main components are Hadoop Distributed
File System (HDFS) and MapReduce.
d. How would you (graphically) identify each of the following ERM components in a
Crow’s Foot model? (8)
Scroll down
