Conformed Dimension Partial Set of Attributes

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Conformed Dimension Partial Set of Attributes

Post  dcow on Wed Nov 11, 2009 9:13 pm

Hi Just looking for some confirmation that a dimension with partial attributes might still be considered conformed. For eample

A dimension of batch

ProdBatch PK
Batch Name
Product ID
Product Name
at an invoice Fact table level with a grain of Lineitem the line item would reference the Prodbatch Surrogate in the batcch dimension

In another datamart Lets Say a Planning datamart The planning iis conducted at the product level

and so my dimension table for products
might be

ProductKey PK
Product ID
Product Name

With each fact referencing product Keys in the Product Dimension.

In this case Product dimension is a subset of the attributes of the Batch dimension . Is this Considered a conformed dimension ?



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Not a conformed dimension

Post  hennie7863 on Thu Nov 12, 2009 4:40 am

Hi Dcow,

In my opinion it's not a conformed dimension. A conformed dimension is a set of data attributes that have been physically implemented in multiple database tables using the same structure, attributes, domain values, definitions and concepts in each implementation.

Why are you asking this? The advantage of conformed dimension in my opinion is 'hopping' from one star to another star by using the same dimension. They are dimension tables in a star schema data mart that adhere to a common structure and therefore allow queries to be executed across star schemas. For example the Calendar dimension is commonly needed in most data marts. By making this Calendar dimension adhere to a single structure regardless of what data mart it is used in your organization you can query by date/time from one data mart to another to another.



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Re: Conformed Dimension Partial Set of Attributes

Post  Andrea Vincenzi on Thu Nov 12, 2009 12:23 pm

Batch is not a dimension, and its attributes should not be mixed with product attributes.
The production of a batch is something that happens at a point in time, so a batch is more a fact than a dimension.
You could model it as a transaction or accumulating snapshot fact depending on it's life span, and connect it to dimensions like product, production date, test date, shipment date, overall quality...
If you find other attributes that belong to the batch, they should be incorporated into a new dimension, leaving batch as a fact. This process is similar to what happens with invoices and shipments.

Andrea Vincenzi

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Re: Conformed Dimension Partial Set of Attributes

Post  ngalemmo on Thu Nov 12, 2009 12:59 pm

No they are not conforming as they are dimensions of two different things. Any fact table at a batch level should also include an FK to the product dimension... this will give you the conformance you need.

I would not replicate product attributes in the batch (although product ID is, most certainly, part of the natural key), since they would be covered by the product dimension. Wither batch is a full dimension or just a degenerate dimension (i.e. putting batch ID as a column in the fact table) depends if a batch has distinct attributes related to it.

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