Hello -- I am taking some excel spreadsheets that are being used to generate some reports and trying to document them as ERD's.
It's been about a year since I took a database course and so am rusty on some concepts.
I have attached some screenshots of my DFD's and the ERD's as they are now. I am wondering if I the ERD's are following proper rules -- specifically related to the subclasses that I have. I have one Superclass
[REPORTS] -- with 5 subclasses. Those subclasses also have some additionaly subclasses. REPORTS has it's attributes which all the other subclasses should have (RID, RName, RDesc, Month, Year, EID) Then the subclasses themselves have several attributes themselves.
A friend of mine said that this isn't correct and that I should just break all the subclasses into their own class...but I think that is wrong. Not sure. I am really wondering if I can get some advice on my ERD's...whether they are correct or need some changes.