Hi Don... how come I never see you anymore?

I think when you say 'ring' people get the wrong idea. The terms
more frequently used are recursive or involuted relationships.

To express this generically in a data model is actually very easy.
It is either:
a M:M relationship between an entity and itself, or (your brand
example)
a 1:M relationship between an entity and itself. (your region
example)
For a long time I have felt like this is one of the top 5 ways a
data modeler can cop-out of his or her responsibility to capture
business rules and the meaning of the data.

What you are wisely struggling with is the bigger question of what
are the rules for a SPECIFIC (not generic) case. I would first
abandon the idea of creating a generic data model. You might
implement a generic physical structure... that is another question.


The critical thing to consider is to what purpose these categories
are being developed. Purpose and meaning are inseparable. If your
clients have more than one purpose, very likely they need more than
one category.

You may find that when you inventory the different purposes that you
have more than one category, each new category will be simpler than
the all-in-one category that you started with.

We, and especially our clients, find this to be counter-intuitive.
They think that more codes is worse than fewer codes. And, "If he
and I are using different codes then how are we ever going to get
any consistency around this place!" The truth is, so long as you
use the same code and code value to do more than one thing then your
consistency is coincidence and you will constantly be struggling
over the stewardship of those codes.

Consider longitude and latitude. Superficially, they do the same
thing and they are expressed similarly. But, each has its own
domain, its own range of values, they behave differently. Imagine
having to use a single set of codes for both... Looking closer have
different purposes. It is a far superior to have two codes that
work together than a single code.

I really should be improving health care...

-----Original Message-----
From: jcm@yahoogroups.com [mailto:jcm@yahoogroups.com]
Sent: Monday, January 31, 2005 5:33 PM
To: jcm@yahoogroups.com
Subject: [JCM] Digest Number 347



There are 3 messages in this issue.

Topics in this digest:

1. Re: generalized ring structures
From: "Thomas B. Cox" <tbcox23@...>
2. RE: generalized ring structures
From: "Tonner, Don E" <don.tonner@...>
3. RE: generalized ring structures
From: "Michael M. Gorman" <mmgorman@...>


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Message: 1
Date: Mon, 31 Jan 2005 09:20:55 -0800 (PST)
From: "Thomas B. Cox" <tbcox23@...>
Subject: Re: generalized ring structures


Please explain a bit more and give some examples of what you mean by
"ring relationships" -- I've heard that phrase used in a variety of
ways.

Thanks.
-Tom

--- tonnerdmhe <don.tonner@...> wrote:

> Hello
>
> I am searching for a generalized logical model for storing a
variety
> of ring relationships. Does anyone know of any such models that
may
> have been published and are available on the web?
>
> Don Tonner
>



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Message: 2
Date: Mon, 31 Jan 2005 12:04:26 -0600
From: "Tonner, Don E" <don.tonner@...>
Subject: RE: generalized ring structures

I am looking for methods of generically storing hierarchies in a
generalized
model. My main object type is 'Category'. 'Categories', if they
had
differentiating attributes, would be sub typed as Brand, Brand
Family, Retail
Groups, which themselves have relationships to other retail groups,
whose
subtypes would be Regional Group, Divisional Group, etc. The ring
relationships
is category to category, or if you refer to the subtypes
specifically, Retail
Group to retail group.

Two separate categories are described below:

A:
1. Brand may be organized into Brand Family.
2. Brand may belong to more than 1 Brand Family.
3. Brand Family may have more than 1 Brand.
B:
1. National Chain may be comprised of many Regional Group.
2. Regional Group may be comprised of many Divisional Group.
3. Division Group may be comprised of sub-divisional Group.
4. etc.
5. National Chain, Regional Group, Divisional Group and
Sub-divisional Group may
group Retail Establishment.
6. For one set of groups:
a) Retail Establishment may only exist once in all the
groups.
b) group may not belong to more than 1 group (is a
consolidation
hierarchy, representing sales rollup, for example)
7. For different set of groups
a) Retail Establishment may exist in many groups.
b) group may belong to many groups (my grouping, your
grouping, we all
have a grouping).

Don Tonner
EAM 5-6501
-----Original Message-----
From: Thomas B. Cox [mailto:tbcox23@...]
Sent: Monday, January 31, 2005 11:21 AM
To: jcm@yahoogroups.com
Cc: Tonner, Don E
Subject: Re: [JCM] generalized ring structures


Please explain a bit more and give some examples of what you mean by
"ring relationships" -- I've heard that phrase used in a variety of
ways.

Thanks.
-Tom

--- tonnerdmhe <don.tonner@...> wrote:

> Hello
>
> I am searching for a generalized logical model for storing a
variety
> of ring relationships. Does anyone know of any such models that
may
> have been published and are available on the web?
>
> Don Tonner
>



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Yahoo! Mail - 250MB free storage. Do more. Manage less.
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Message: 3
Date: Mon, 31 Jan 2005 14:38:24 -0500
From: "Michael M. Gorman" <mmgorman@...>
Subject: RE: generalized ring structures

At 01:04 PM 1/31/2005, you wrote:
>I am looking for methods of generically storing hierarchies in a
generalized
>model.

~~~~~~~~~~~~~

The attached might help. We have single file hierarchies, multiple
file
hierarchies, and Bills-of-Materials in our metabase application.

Regards,
Mike Gorman


[This message contained attachments]



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