Grading for Project 1
CS 317
Spring 2005

ER Diagram: 40%
Relationships: 40%
Write-up: 20%


The following were correct solutions for implementing leases entity sets:
- leases as root entity set
  - flat lease isa lease
  - room lease isa lease
- student as root entity set
  - student leasing flat isa student
  - student leasing room isa student

The following were common problems and issues:
- students lost at least 10-20 points if they didn't set up leases correctly
- lease as a relationship between students, halls and flats
  - lease has key of lease#, not allowed in a relationship
  - misunderstanding - relationship must hold among all involved entity sets
    - student isn't involved with both a flat and room
- leases as root, residence hall isa lease, student flat isa lease
  - most common problem
  - use isa only when something "is a" type of something else
  - residence hall and flats aren't leases
  - what does it mean to "inspect" a flat lease?
- university housing with halls and flats as sub-types
  - hall should be kept separately; otherwise each student's lease redundantly records all hall info
  - no way to access particular room with this approach
- leases, invoices and students in three-way relationship
  - no points off, but this is undesirable - requires invoices be set when lease is created


Here's the list of problems and the corresponding points deducted for each. Problems ending in a ":" were followed by a name or phrase explaining the problem. These cover about 90% of the points deducted.

-10 no entity set for lease
-10 no table for lease
-10 leases as root, residence hall isa lease, student flat isa lease
-10 no connection to flats/rooms from leases
-10 incorrect three-way relationship between leases, flats and halls
-5 rooms not represented separately from residence halls
-5 residence hall info represented redundantly
-5 flat info represented redundantly
-5 lease has relationships to both flats and rooms
-5 student connects to both flat and room without mention of null fields approach
-5 lease has flat# and place# without mention of null fields approach
-3 missing minor table: 
-3 student leases entire residence hall
-3 no connection to flats from inspections
-3 no connection to leases from invoices
-3 incorrect three-way relationships:
-3 incorrect ISAs:
-2 student lives in hall not room
-2 inspection is relationship not entity set
-2 redundant table: 
-1 inspection date not part of inspection key
-1 incorrect keys:
-1 separate table for many-to-one or one-to-one relationship:
-1 table has incorrect multiplicity relationships: 
-1 incorrect multiplicity: 
-1 incorrect entity set:
-1 redundant relationship: 
-1 missing relationship: 
-1 incorrect relationship: 
-1 missing attributes: 
-1 extra attributes: 
-1 redundant table fields:
-1 student doesn't have multiple leases (past, present, and future)

-15 no writeup
-2 no explanation of how subtype was converted: 

+5 to +15 for Extra Credit