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CS 511 Database Management System - Homework 1, Assignments of Deductive Database Systems

University of Illinois - Urbana-ChampaignDeductive Database Systems

Information about a university homework assignment for a database management system course. The assignment includes four problems related to the relational data model, array-based data modeling, null values in boolean columns, and r-tree indexing for high dimensional data. Students are required to submit hard copies of their solutions and email digital copies to the ta.

Typology: Assignments

Pre 2010

Uploaded on 03/11/2009

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CS 511 Design of Database Management System
Homework 1
Due: 2:00 PM CST on September 12, 2007
NOTE:Please submit a hard copy of your homework. Bring it to the lecture table at the
beginning of the lecture on 12th September, 2007. The hard copy should be as clearly
readable as possible. You may be subtracted points for unreadability and ugly
presentation.
I2CS Students: You should email your solutions to the TA([email protected]) in the
pdf or the word format. Please send your email with subject “CS511-HW1” and solution
file attached by 2PM UIUC time (CST).
Problem 1: Relational Model [20 Pts]
Briefly mention two flaws of the relational data model.
Relational model has bunch of shortcomings. For instance:
1) The relational model is not flexible enough to capture various formats of
relationships among data in real application like semi structured data.
2) Since model is quite complicated itself and recommends normalization, its
performance is relatively lower than simple file based models.
3) It does not support customized operations for complex data types.
Problem 2: Relational Model [30 Pts]
Scientists use multiple sensors to gather temperature information of a specific object in
scientific observations in order to obtain exact result. Each sensor observes temperature
information every second, and sends the data to the main server to be stored on specific
times. A sensor would sometime report nothing (null value) or wrong value due to the
physical problems. Scientists have to use data from all sensors to find out the most
precise temperature at each time. Hence, they merge and take average of the observed
data for each time spot. They also compute differences among data gathered in different
times, or compound them to see temperature behavior during longer time period. One
dimensional array is a good fit to represent this data. Specify and formulate an exact
data model to represent the data and an algebra that covers the required operations. You
could add additional data item(s) to the array structure in your model.
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CS 511 Design of Database Management System

Homework 1

Due: 2:00 PM CST on September 12, 2007

NOTE : Please submit a hard copy of your homework. Bring it to the lecture table at the beginning of the lecture on 12th September, 2007. The hard copy should be as clearly readable as possible. You may be subtracted points for unreadability and ugly presentation.

I2CS Students : You should email your solutions to the TA([email protected]) in the pdf or the word format. Please send your email with subject “ CS511-HW1 ” and solution file attached by 2PM UIUC time (CST).

Problem 1: Relational Model [20 Pts]

Briefly mention two flaws of the relational data model.

Relational model has bunch of shortcomings. For instance:

  1. The relational model is not flexible enough to capture various formats of relationships among data in real application like semi structured data.
  2. Since model is quite complicated itself and recommends normalization, its performance is relatively lower than simple file based models.
  3. It does not support customized operations for complex data types.

Problem 2: Relational Model [30 Pts]

Scientists use multiple sensors to gather temperature information of a specific object in scientific observations in order to obtain exact result. Each sensor observes temperature information every second, and sends the data to the main server to be stored on specific times. A sensor would sometime report nothing (null value) or wrong value due to the physical problems. Scientists have to use data from all sensors to find out the most precise temperature at each time. Hence, they merge and take average of the observed data for each time spot. They also compute differences among data gathered in different times, or compound them to see temperature behavior during longer time period. One dimensional array is a good fit to represent this data. Specify and formulate an exact data model to represent the data and an algebra that covers the required operations. You could add additional data item(s) to the array structure in your model.

Problem asks for array based model. In this model the basic elements instead of relation, is one dimensional array. Each observation could be modeled by an array A [N+M], which stores observations over N time steps. Extra M element could be used to store information like the starting time of observation and so on. We use just the observation start time here. In order to cover the final operations we will need the following basic operations:

  1. Value Selection S(A, i ) : Given array name and element index, returns value stored in the index. Using this operator a new operator called Time Selection ST(A) could be defined which given array name returns starting time period of observation.
  2. Compound C(A,B): Given two arrays with consecutive observation time period, returns a new array whose size is sum of the input arrays and its starting time is the smaller input starting time.
  3. Valid VA(value): Given a value decides if it is valid. A value is valid if it is in a specified range of values [MIN, MAX], or not null.
  4. Basic mathematical operations among numbers

It is easy to show that having a database management system based on the above model; the required operations could be implemented. We can formulate the required operations like difference among two arrays as basic operations, but it is redundant.

Obviously there could be various solutions for this problem. The solutions that had redundant operations were given complete points. Relation based models were given complete points as well.

Problem 3: System R [30 Pts]

In relational database management systems like system R when user does not assign any value to a column in a row, it is tagged by especial value called null. 1- Give two different interpretations of having a null value in a column of type Boolean. 2- Logical conjunction ( AND ) and logical disjunction ( OR ) consider just true and false as their input and output values. For each interpretation in previous part, create a new truth table for those operations that includes null value.

  1. NULL could represent any value in the domain, which user does not know about at the time of data entry, for instance if an employee is older than 25. Therefore it complies with the properties of Boolean algebra.

Operand 1 Operand 2 AND OR TRUE NULL NULL TRUE FALSE NULL FALSE NULL NULL NULL NULL NULL