E-R Diagram (1 Viewer)

[TaiChi56]

I am working on an E-R Diagram and I am not quite sure on a certain relationship. Here is what I have.

I am showing a relationship between Service and Subproperty. Management wants to have the service they provide tracked by the subproperty, not the property itself.

So I am showing a One-to-One Binary relationship. I am saying that for every one service there is one subproperty. But then I started thinking that this would be wrong.

One property can be broken down to front lawn, back lawn, side garden, so forth, which would be the subproperty. Which means that one service bill for a customer could cover all these, but I would probably relate it to the property on the billing. Relating the service to the subproperty would be a One-to-Many Binary relationship. Am I correct or off target? Any help would be appreciated. Thank you.

P.S. The table goes from Property to Subproperty and Service is only linked to Subproperty.

 

[Pat Hartman]

This sounds a little like the kits problem in a manufacturing system. Parts may be sold by themselves or as part of a kit. You need to have a table of all services. That means that if you sell "back yard only", that has to be a service. You can use the subproperty to break down services that are sold as a "kit". That means that some services will have subproperties and some will not.