Member Avatar for delbertkay

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.

libraryerddani.doc (1309.5 KB)
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Member Avatar for timothybard

I reviewed your ERD and everything looks good. my initial thought was that, if the subclasses were similar enough, then perhaps you could combine some of the subclasses into one class and just have an attribute that tracks the type of subclass it is. For example, the subclasses of the government-publications appear to be very similar. However, after looking at the ERD more closely, it appears that the subclasses may be different enough to merit being subclasses. The only reason I mention this is because any combine you do can make things more straight-forward and make this easier to design and program. However, you are more familiar with the data, so you would be in a better position to make any determinations.

THe ERD looks good, but without knowing what the data is like, it's hard for me to give you specific thoughts.

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