[Top] [All Lists]

Re: [ontolog-forum] Is there something I missed?

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Mitch Harris <maharri@xxxxxxxxx>
Date: Fri, 30 Jan 2009 15:17:51 -0500
Message-id: <553db06d0901301217m74e6d416wb840b9d3166d2718@xxxxxxxxxxxxxx>
On Fri, Jan 30, 2009 at 2:46 PM, Schiffel, Jeffrey A
<jeffrey.a.schiffel@xxxxxxxxxx> wrote:
>> From: Patrick Cassidy
>> In the RDB's I have seen, each field (column in a table) often
> (typically?)
>> represents one relation on the type represented by the table, so the
> number
>> of columns does not have any relation to the arity of the relations
> used.
>> Two or more columns can be used together to represent higher-arity
>> relations, but they may be quite independent.
> I'm not certain I know what you mean. In an entity-relationship isn't
> the relation the entire row, not just one column? The entity is the name
> of the table. The names of the columns are the identifiers of an n-ary
> relation. Each row is an instance of the n-ary relation.    (01)

Yes to all of those.    (02)

> Or am I missing something?    (03)

I think PC's point is that it is -possible- to extract lower arity
relations from a large arity one.    (04)

My point, which is not contradictory to that, is that -most- db
tables/relations I see are spelled out as ternary or greater, whatever
the relations that it -could- be reduced to.    (05)

But reverse direction point of mine is that whatever the cogency of a
database is to a human reader, one can still artificially reduce the
max arity, and still preserve...let me see...correctness.    (06)

(I'm just trying to be explicit about technical meanings of words
-and- real world experience).    (07)

Mitch    (08)

Message Archives: http://ontolog.cim3.net/forum/ontolog-forum/  
Config Subscr: http://ontolog.cim3.net/mailman/listinfo/ontolog-forum/  
Unsubscribe: mailto:ontolog-forum-leave@xxxxxxxxxxxxxxxx
Shared Files: http://ontolog.cim3.net/file/
Community Wiki: http://ontolog.cim3.net/wiki/ 
To join: http://ontolog.cim3.net/cgi-bin/wiki.pl?WikiHomePage#nid1J
To Post: mailto:ontolog-forum@xxxxxxxxxxxxxxxx    (09)

<Prev in Thread] Current Thread [Next in Thread>