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One or two dimensions?

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One or two dimensions? Empty One or two dimensions?

Post  Seddryck Tue May 10, 2011 4:01 pm

We have an issue with our Customer, he doesn't agree with our dimensional model. To illustrate our conflict, we recommend to have two dimensions, one for employees and another for customers (customers are companies not humans). He doesn't agree and wants one dimension mixing both concepts. Not a junk dimension where we perform a cross join between the two concepts but a kind of union where we add the two concepts.

We've illustrated that all facts are linked to only one of both concepts meaning that for all facts half of the dimension is not used. Not a problem for them, by default excel doesn't display members without fact associated. They argue that both concepts are sharing a few attributes (display name, ...) but we've already argue that other dimensions are also sharing these attributes. In fact problem's root is that a long time ago someone has modeled the operational application mixing both entities. So they are arguing that business people are used to the mix of both concepts ... But on our side we know it's a bad design to mix them.

Now our last chance sounds to be able to explain an analysis that they will not be able to perform if the design implements only one dimension and not two. Someone has an idea of analysis not possible due to this bad design?



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One or two dimensions? Empty Re: One or two dimensions?

Post  BoxesAndLines Wed May 11, 2011 10:11 pm

They are different concepts. They are not hierarchies. It's not whether the two entities share the same named attributes, it's whether the entities share the same meaning (or semantics seems to be the buzzword this week). Keep them separate.

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