Re: Multivariate relation (Was topological databases)

On Tuesday, January 27, 2015 at 5:50:48 PM UTC-8, Derek Asirvadem wrote:
> Tegiri
> Can you please provide a one line definition of a multivariate relation. Google finds nothing in this space, only such that is related to multiple regression..

Section 3.2 from the Alice book
http://wiki.epfl.ch/provenance2011/documents/foundations+of+databases-abiteboul-1995.pdf reads:

"Under the named perspective, these attributes are viewed as an explicit part of a database schema and may be used (e.g., by query languages and dependencies). Under the unnamed perspective, the specific attributes in the sort of a relation name are ignored, and only the arity of a relation schema is available (e.g., to query languages). "

Unnamed perspective is something that has been used in mathematics for a long long time. Please note that Tarski's algebra of binary relations also uses unnamed perspective. It seems that only after Codd's invention of relational model the named perspective reigned supreme, so that database practitioners might be even not aware of relations with unnamed/positional attributes. In those rare cases where SQL uses positional notation, it is more of misnomer. Compare

select name from employees order by 1

with

select name from employees order by 1.000001

Apparently, a person who originally designed SQL "order by" clause was not familiar with continuous functions.

Getting back to your question, the term "multivariate relation" is synonym for "relation with named attributes", which emphasizes named perspective. Received on Wed Jan 28 2015 - 05:40:59 CET