Question

What is a modification problem? What are the three possible types of modification problems? Please explain in depth.

Answer 1

Modification problems are the problems that are encountered when we try to make changes in the List. They happen when we try to update some value, delete some value or add some value. Correspondingly there are three types of modification problem: 1. Updating some value in the list 2. Deleting some value from the list 3. Adding some value to the list Consider the table 1 shown below: Student Name Advisor Name Advisor Email Id Rahul Andrew [email protected] [email protected] Tony Twain Bing [email protected]

1. Updating some value in the list: Suppose we want to update the email id for adviscr Bing. Then if we update this value in third row but not in second row then our data will be inconsistent. Therefore we need to update this value everywhere in the list where it appears. Not doing this will lead to inconsistency 2. Deleting some value from the list: Suppose we want to delete the data of Rahul. If we do this then we also have to delete data of Advisor Andrew because he is advisor of only single student. 3. Adding some value to the list: Suppose there is a advisor Thomas and we want to add his data but here we are unable to do so because he is not mentoring even a single student. So we are unable to capture the data of those advisors who are not mentoring any student