Section 8
When modeling historical data
the unique identifier is always made up of a barred relationship from the
original two entities. True or False?
True
False
(*)
Modeling historical data can
produce a unique identifier that includes a date. True or False?
True
(*)
False
Which of the following
scenarios should be modeled so that historical data is kept? (Choose two)
LIBRARY
and BOOK (*)
STUDENT
and GRADE (*)
LIBRARY
and NUMBER OF BOOKS
STUDENT
and AGE
Which of the following is a
logical constraint that could result from considering how time impacts an
example of data storage?
Dates
must be stored with Time.
End
Date must be before the Start Date.
An
ASSIGNMENT may only refer to an EMPLOYEE with a valid employee record at the
Start Date of the ASSIGNMENT. (*)
EMPLOYEE
periods can overlap causing the database to crash.
All systems must include
functionality to provide logging or journaling in conceptual data models. True
or False?
True
False
(*)
What is the function of logging or journaling in conceptual data
models?
Allows
you to track the history of attribute values, relationships, and/or entire
entities (*)
Creates
a fixed time for all events in a data model.
Gives a
timestamp to all entities.
Represents
entities as time in the data model.
You must make sure all entities
of a proposed system can fit onto one diagram. It is not allowed to break up a
data model into more than one diagram. True or False?
True
False
(*)
There is no point in trying to
group your entities together on your diagram according to volume, and making a
diagram look nice is a waste of time. True or False?
True
False
(*)
No formal rules exist for
drawing ERD's. The most important thing is to make sure that all entities,
attributes, and relationships are documented on the diagram, and the diagram is
clear and readable. True or False?
True
(*)
False
Which of the following statements
are true for ERD's to enhance their readability. (Choose Two)
Avoid
crossing one relationship line with another. (*)
You
must ensure that you have every single entity--even if hundreds of them
exist--on one single, big diagram.
The
crows feet (many ends) can point whichever way is the easiest to draw.
It is
OK to break down a large ERD into subsets of the overall picture. By doing so,
you end up with more than one ERD that, taken together, documents the entire
system. (*)
When a relationship may or may not be transferable,
depending on time, this is know as a/an:
Non-transferable
Relationship.
Arc.
Conditional
Non-transferable Relationship. (*)
Transferable
Relationship
How do you know when to use the
different types of time in your design?
You
would first determine the existence of the concept of time and map it against the
Greenwich Mean Time.
It
depends on the functional needs of the system . (*)
Always
model time; you can take it out later if it is not needed.
The
rules are fixed and should be followed.
All systems must have an entity
called WEEK with a holiday attribute so that you know when to give employees a
holiday. True or False?
True
False
(*)
Which of the following would be a
logical constraint when modeling time for a City entity?
Cites
may change their names and/or country association if the borders of a country
change. (*)
If you
are doing a system for any French City, you would need security clearance.
Daily
traffic patterns must be monitored to determine how many law enforcement
officers are needed.
People
are born in the city and people die in the city.
If you have an entity with a DATE
attribute, in addition to other attributes that track date characteristics, you
should create a DAY entity. True or False?
True
(*)
False
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