Re: Sensible and NonsenSQL Aspects of the NoSQL Hoopla

On 01/09/2013 11:38 PM, karl.scheurer_at_o2online.de wrote:
> Am Sonntag, 1. September 2013 19:49:48 UTC+2 schrieb Eric:
...
>> Ordering and grouping are not part of the data definition, they are
>> operations.
>
> Grouping are part of the data definition:
>
> employes are a set of (teachers, assistents, secretaries ...)
>
> Every set with potential subsets can be defined with groups
>

This pretends that a predicate that is about individuals is the same as a predicate about sets of individuals. Tuple elements that are sets aren't the same thing as tuples that are sets.

Not every group can be ungrouped, which should be enough to show that the grouped relation can't possibly have the same predicate as the ungrouped one. If the predicates must be different then the two data definitions aren't defining the same thing, so you are talking apples and oranges.

As far as I can tell, the RM doesn't prevent its own application in an implementation that chooses to equate grouped relations with ungrouped ones, eg., where the empty set as a value of an attribute is considered meaningless so that every such attribute-set-value can be expressed/recorded as a set of singleton sets. Received on Mon Sep 02 2013 - 17:30:42 CEST