- Professors have a SSN, name, age, rank and research specialty
SSN name age rank research specialty
--- | / / /
\ | / / /
--------------------
| Professor |
--------------------
- Projects have a project number, a start and end date, a budget
Pnum start end budget
---- / / /
\ / / /
-------------------
| Project |
-------------------
- Students have a SSN, name, age, and year
SSN name age year
--- \ / /
\ \ / /
------------------
| Student |
------------------
- Each project is managed by one professor (the principle investigator)
(6) Professors can manage and/or work on multiple projects
Pnum start end budget SSN name ...
---- / / / --- /
------------------- / \ ------------
| Project | =========>> < Managed By > ----- | Professor |
------------------- \ / -------------
- Each project is worked on by one or more professors (co-investigators)
- Professors can manage and/or work on multiple projects
Pnum start end budget SSN name ...
---- / / / --- /
------------------- / \ ------------
| Project | =========== < Worked on By > ----- | Professor |
------------------- \ / -------------
- Each project is worked on by one or more students
Pnum start end budget SSN name ...
---- / / / --- /
------------------- / \ ---------
| Project | =========== < Works On > ----- | Student |
------------------- \ / ---------
Q: why not have a single Worked On Relationship set involving Project, Student and Professor entities?