> If an > >attribute is missing then you will have an invalid data type. > > > >Therefore, if an attribute is allowed to be missing then the relations > >have not been properly constructed in the model. > > > >In clinical applications there are MANY MANY places where this problem > >exists (especially regarding temporal data). So, in most cases every > >attribute (if you insist on using a relational model) in a clinical > >system should be decomposed into 6NF (a key and a column). > > > >Otherwise your relations aren't atomic and your application code must be > >created to handle these exceptions.
testing for null isn't that hard, happens all the time when doing application programming, especially in java, for some reason. Java (and others) have a null object pattern , so the infamous NullPointerException doesn't choke a program so frequenty, may be a Null row for the relational model ? ;) > Therefore, why constrain yourself > >with a data model (relational) that doesn't fit anyway? because it's cheap , there's no lock-in, and widely understood ( SQL, at least when people avoid using dialect features). _______________________________________________ Gnumed-devel mailing list [email protected] http://lists.gnu.org/mailman/listinfo/gnumed-devel
