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Tip of the Day
Language: SQL Server
Expertise: Beginner
Jun 28, 1999

Business Rules and Semantic Object Models

Question:
What are business rules in relation to a DBMS. Do you have any posssible examples for a university database?

Also: Do you have any hints to drawing a Semantic Object Model for a relationship between A university, its three campuses, donors of funds, students and staff?

Answer:
Business rules are constraints; they could be things like NOT NULL, or CHECK or RULE, or more exotically, a foreign key. There is a distinction to be made between a business rule that is used to enforce housekeeping versus ensuring referential integrity. What if our rule says that Student SSN cannot be Null. If we are entering student data and SSN is not key and we're almost done but have no SSN, should the entry be allowed?

My point is that this kind of validity checking may be more profitably spent on the front end, before it gets to the server, where I will enforce the NOT NULL constraint only on my key columns, for example, or failing that, then be sure to declare defaults for all NOT NULL columns.

Possible business rules for a university database may be that: no student can register for less that twelve credits a semester; no student can register for more than thirty credits a semester; tenured faculty members have a choice of a parking space or a train pass but not both.

As to the second question, take a look at Conceptual Schema and Relational Design by Terry Halpin, then go check out Visio Enterprise 5.0

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