Re: 1 NF

>> I read an interview with Chris Date (http://www.dbmsmag.com/int9410.html) which made me a little bit confused. He claims that having an array as a column values doesn't violates 1NF. Is this the common opinion at comp.databases.theory too? <<

Pretty much, if you can ser up the rules for arrays so that they form a Domain, in a relational sense. I would need to have rules for manipulating them, but most important I need Theta Opertors which can be used to define JOINs with columns in those domains.

There is also a difference berween "atomic" and "scalar" in the definition of 1NF. For example (longitude, latitude) is atomic (Greek for "without parts" or indivisible) because it resolves to one point in space. But longitude and latitude are scalar values by themeselves (I can go into scales and measurements, but the idea is a set of discrete values, a way to assign a value to an event, blah, blah).

>> Does a blob containing an image violates 1NF? <<

There is hard! Can you break it down into meaning parts -- i.e. is the blob atomic? That one is hard, since pictures have semantic content -- "Look!! There is Lindsay Lohan behind a tree!" but it is really hard to use theta operators because semantics lead to fuzzy logic. So I would say that the fuzzy logic would override the usual 3VL for RDBMS and we do not have a proper domain. Received on Wed Feb 28 2007 - 21:02:27 CET