1
vote
5answers
247 views

object model and data model

I have heard/read mixed things on whether to start with an object model or a data model. And more people say to starting with an object model as it will ease your data modelling. My question is, ...
1
vote
1answer
788 views

What is the difference between UML Data profile and ER model?

I have been asked this question and even after a lot of research, I cannot find the answer. When I design a database using Entity relationship (ER) and then re-draw it as UML class model (extended ...
1
vote
1answer
2k views

How to model/structure data that contains parent/child relationships for the same entity?

I think it is just my thinking that is off here. Suppose I have two entities: question and choice. A question can be a parent or child, or both (in relation to other questions). It seems that this ...
3
votes
2answers
136 views

Does this situation call for well specified associations, single table inheritance, or polymorphic association?

I'm building a web-app where users can keep track of who owes whom money. I have users and debts. Given a user I want to be able to find out all the debts to other users, and all the loans to other ...
2
votes
2answers
224 views

how to model this relationship ? in ERD

I have three entities : Technician Vehicle Repair The question is how to model this in ERD? Knowing that a technician can repair multiple cars, and the same car can be repaired by one and only one ...
3
votes
2answers
122 views

Best Way to Express Meta-Info on Missing Data?

I work in healthcare IT, reviewing data management processes of various observational studies. One problem I have repeatedly faced is the poorly encoded data, especially when some values are missing. ...