Multivalued attribute on Dimension

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Multivalued attribute on Dimension

Post  RobLL on Mon Jan 27, 2014 8:56 am

I would like to know how to model this. I've searched the forums and the Data Warehouse Tooolkit but don't see it covered.
I have a Product dimension with a multi-valued attribute called Characteristic. There are 25 characteristics currently. A given product could have anything between zero and many of theses characteristics. Queries/reports may constrain on this attribute.

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Re: Multivalued attribute on Dimension

Post  RobLL on Mon Jan 27, 2014 10:48 am

Just to add to my question...
I have found in the Data Warehouse Toolkit (second edition), page 205, the highlighted statement, "An open-ended many-valued attribute can be associated with a dimension row by using a bridge table to associate the many-valued attributes with the dimension." However, the example is all about associating many customers to an account by putting a bridge table between a Customer Dimension Table and an Account Dimension table. The fact is just associated with the Account Dimension. I can see the point of this where the Customer Dimension has more than one attribute. Is a simpler approach possible in the scenario I described in my original post? Do I need a Product Characteristic Dimension that just holds a surrogate primary key and the attribute 'Characteristic'? Can't I dispense with the Product Characteristic Dimension and bridge table and, instead, just have a Product Characteristic table that has a many to one relationship with the Product Dimension?

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Re: Multivalued attribute on Dimension

Post  BoxesAndLines on Mon Jan 27, 2014 11:01 am

Characteristics are meaningless from a product reporting perspective. What is meaningful is color, size, weight, etc. What I would attempt to do is to undo the OLTP EAV (entity attribute value) model and build a product dimension(s) to support the various product characteristics. For example, if "Color" is a characteristic, create a Color dimension to allow filtering of metrics by color.
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Re: Multivalued attribute on Dimension

Post  RobLL on Mon Jan 27, 2014 12:55 pm

Here are some of the characteristics: telescopic arms, sprung pads, ultraflex, folding frame, comfort bridge. The list will be added to as new characteristics are developed. For any given product, the characteristic is either present or not present. Your suggestion is reasonable but does not suit this scenario.

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Re: Multivalued attribute on Dimension

Post  ngalemmo on Mon Jan 27, 2014 5:56 pm

Have a characteristic dimension and a bridge. Don't take shortcuts.

Once you have it implemented, the next step in the evolution of its use would be to add attributes classifying the various characteristics. That is much easier to do if you build a characteristic dimension table.
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