"Let's say that a database lists that a person has had a car insurance since 1967 while the same database lists the person's age as 18 years. Syntactically, there are no errors in the database, but semantically we should be able to diagnose the inconsistency here."
And someone will have to go through and fix the inconsistency - yeah, right. The software will be written to make some kind of semi-educated guess from its Artificial Stupidity engine, and change one of the data to make the database consistent. And all of a sudden, the IRS is knocking on some poor kid's dorm room, asking where his 1040s for 1980-2000 are, since he obviously had enough money to pay for car insurance. Reality will not matter - the computer says, the computer is right, pay up.