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The main issue with this subset constraint is not the join path, which is trivial in this case and will be filled in by NORMA. The issue is that your roles aren't compatible, which needs to happen as a prerequisite for any join path. The subset sequence (sequence 2 in NORMA) has LegalEntity and Address roles, whereas the ...
I read Section 10.1 again and saw diagrams 10.4(a) and 10.5(a). I think I understand the idea captured in these diagrams now. The highlighting was very helpful in explaining the concepts. I also did not realize that it made sense to connect either end of the subset constraint to multiple roles at the same time. Again, the highlighting in the ...
The constraints you need are called join-subset constraints. These are discussed in Section 10.1 of "The Big Brown Book".
I've tried to attach a diagram for the "Employee works in Building" example, but it doesn't appear in my Post window. If you can see the diagram, then notice that ...
Sorry the formatting was lost on my original post--not sure why.
I am attaching two JPGs in two messages. The first illustrates three examples where consistency constraints are (in my opinion) progressively harder to illustrate. The second image is the same idea, but now with objectified relationships.
Yes, you describe a requirement that is common to many organizations.
It would help a lot if you could post the object-role model on which you are working.
One way is to make a .png or .jpg picture from NORMA and use the "File Attachment add/update option to upload the file.
Can you do this?
Here is an example
Our use of ORM to help business and technical teams share a common language of concepts is taking off. ORM does just what I need it to do--help us focus on the concepts and not the details.
I have run into a situation over and over, and I have never been able to model it satisfactorily. I usually end up adding a business rule note instead. ...
Clifford's suggestion is generally how I do it in SQL. I'd just prefer not to put a "dummy" attribute (x) in the model simply in order to express this constraint. A cardinality constraint is more concise. An alternative would be to have some way to specify a uniqueness constraint without any associated values - in relational ...
[quote user="Terry Halpin"]That's a neat trick[/quote]
it's a trick, but it's not just a trick. It reflects the fact that every model exists in some context, and a thing that's a singleton in one context may have counterparts in other contexts. This approach merely makes the contextualisation explicit by encoding the ...
That's a neat trick, and it will work so long as (a) the CPI Authority itself is immutable, and (b) you know the CPI Authority. If either of those assumptions doesn't hold, then you are going to need a cardinality constraint.
I'd prefer to add support for cardinality constraints in the relevant ORM tool, as I think ...