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Rolemo
For uniformity, we decided to make the rules for objectified associations the same as for normal object types (by default, an object type is not independent). Suppose you had a schema consisting of just the fact type "Person(.id) was born in Country(.code)". By default, Person and country are not independent, so their roles ...
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Rolemo
It sounds like you have a mandatory, n:1 fact type "Employee(.id) has PermissionLevel(.name)" with the value constraint {'Organization', 'Region', 'Country'} on PermissionLevel.
Adding subsetting doesn't help. You need to specify elsewhere what semantics you attach to these levels. Depending on ...
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Rolemo
For this example, I would choose to make the fact type "Project is completed" as simply derived. The subset constraint approach would create an extra Boolean column "isCompleted" which would then have to be kept in sync with the completionDate column (isCompleted set to true/false if completionDate is not-null/null). It ...
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Apparently you are using an old version of Lab 4. We changed the way subtyping works so that now a solid arrow is always used if that path provides a way to the preferred identifier. I just sent Ken the latest version of Lab 4 which he should place soon in the library. This shows solid arrows, as you are experiencing.
Cheers
Terry
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Rolemo, download NORMA Lab 5 from the library and see the slides on the report generator. You can generate a report with the model verbalized for clinet to approve.
Cheers
Terry
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Rolemo
I assume you want to use "exists" as a unary predicate. The formalization of ORM instead always uses an existential quantifier instead of a predicate for asserting existence. So please do not use "exists" as a predicate.
Cheers
Terry
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Hi Rolemo
In this example, EmpNr is the identifier for Employee. If you declare a reference mode for an entity type, that provides its preferred identifier. The expression Academic(.empNr) is short for the 1:1 mandatory existential fact type "Academic has / is of EmpNr()".
Cheers
Terry
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Hi Rolemo
Facts may be compound or atomic. Atomic facts can't be rephrased as a conjunction of 2 or more smaller facts without information loss (with the same objects involved). Atomic facts are either elementary facts or existentail facts. Elementary facts apply a logical predicate to one or more objects, e.g.
The Country identified by the ...
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Rolemo
Your ternray is correct as is. There are two constraints on it (a mandatory role constraint and a uniqueness constarint). When you combine the meaning of these constraints you obtain the meaning you were after (corresponding to a multiplicity constraint of 1 in UML -- we don't use UML's multiplicity constraint notation because ...