CS336 Principles of Database Management Systems
Problem Set 1
Due: February 14, 2002
- 1.
- Suppose that you have been asked to develop a ``telephone book''
application for a digital cellular phone. The purpose of the
application would be to store names, telephone numbers, type of phone
(home, work, cell, etc.) and other information, on the device. Phone
numbers will be used both for making outgoing calls and for
identifying incoming phone numbers.
Please write brief, clear answers of a few sentences in length for
each of the following:
- (a)
- What additional information would you need to know to determine
whether or not to use a database management system (DBMS) in
implementing this application? What features of a DBMS might be most
desirable?
- (b)
- What if part of the requirement for this application is to be
able to easily backup and exchange phone book information with other
phones through a centralized server that everyone can connect to
periodically? How would that affect your decision?
- (c)
- What characteristics of a DBMS would discourage you from
recommending using one in this application? Consider specifically the
possible limitations of the device the application will be running on.
- 2.
- Suppose you have a 1000-cylinder disk with the following performance
characteristics:
| Max Seek |
Rotational |
| Time |
Speed |
| 15 mSec |
7200 RPM |
- (a)
- What will the average access time be for completely random access
(for each read, there is a uniform probability that the read will be
to any track)?
- (b)
- What will the average access time be, for purely sequential
access (for each read, there will be a seek of 1 track)?
- (c)
- What will the average access time be if we know in advance that
the average seek distance will be 100 tracks?
- 3.
- You have been hired as a summer intern by TIC (Three Initial
Corporation). The top management of TIC are very concerned about the
erosion of corporate profits caused by employee pilfering from the
office supplies cabinets, and they want you to implement a database to
track supply usage.
After consultation with people throughout the company, you arrive at
the following initial conceptual design for the database. Attributes
are italicized.
- Entities:
- Item An item has a Stock_Number that uniquely
identifies it. It has a description, e.g. ``BIC medium
ball-point pen'' and a supplier (there may be more than one)
- Location A location has a unique Location_code; a
Location_description; and a Secretary - the name of the
person with the key to this location (one per location).
- Relationships:
- Stocked An item is Stocked in a location.
Some Quantity of this item is stocked in the location.
- Constraints:
- Items may be stocked in several locations, but must be stocked
in at least one location. Locations may stock several items, but need
not stock any (an unused supply cabinet is OK).
Draw an Entity-Relationship (E-R) diagram for this conceptual
design. Be sure to show all entities, relationships, attributes
(indicate if any are multi-valued, and identify which form the primary
key), and relationship constraints (mapping cardinalities and
participation).
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Jack Keane
2002-02-02