Assignments/Exercises

Take a close look at the ER model in Figure 1, “Example of an ER Model”. Answer the following questions.

  1. How many pages does a site (root) allow, and why?
  2. What happens if someone inserts an extra page into the database referring to a given site? Why?
  3. Links of type 'A' constitute the main navigation. What happens if a page is inserted without a link to it from the front page?
  4. Can you insert a link from the front page to a page that does not exist? Reason?
  5. May an image be used on more pages simultaneously? Reason?
  6. Is it possible to limit the listing of pages to those belonging to a specific root? Please use your imagination and try to figure out how?
  7. Is it possible to write site name at the top of the display of each page belonging to the site. If yes, how?

A school or a college wants an IT system holding classes among other information areas. The admin office would like to be able to print lists of the students from a class. They must show names, addresses, email addresses, etc. They must also be able to see which teacher teaches what subject in any class. The students would like the system to tell them what teacher they are facing in any given subject. Design an ER model and discuss it.

The local census bureau has been asked by the tax people for information about marriages in a given year. They want to know who married who and when. The list must uniquely identify the persons, their names and addresses. Please design the appropriate ER model and discuss it.