Re: What gives data meaning?

frebe wrote:
<snip>
If you think about it, neither zip code means anything to the database.
They're simply characters in a field.


With a proper type system or check contraints, a RDBMS could guarantee
that no invalid zip codes are stored into the database. If we want to
store zip codes for multiple countries, one solution is to have
different relations for different countries with different domains/
types for the zip code attributes.

But you quickly approach the DB designer's version of Heisenberg's
uncertainty principle. How does the DB know it has all zip code formats
to test against? How does it know what all the valid zip codes are? As
soon as it's measured and implemented how does the DB know a new zip
code wasn't created in some growing suburb of Zurich?

As the DB more rigorously guards what it can not be certain of, it
creates obstacles, bugs, or simply starts getting in the way of people
who are certain of what they're doing.

Is there some definite point beyond which a DB designer should stop
creating constraints? Is there a point of diminishing returns? How
much effort should be asserted to know the exact value, set of values,
and potential values of every field in the database? At some point
mightn't even the post office shrug its shoulders and deliver a letter
to a destination country and let them figure-out its address if they
don't recognize anything but the country?


--
Visit <http://blogs.instreamfinancial.com/anything.php>
to read my rants on technology and the finance industry.
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