coping with an attribute definition change

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coping with an attribute definition change

Post  RoyalWulf on Sun Dec 07, 2014 11:38 pm

I have two dimensions
Course Info - has attributes about a course
Student Funding - this has attributes about how a student is funded depending on the type of student and the course they are enrolled in.

There is a desire for the definition of an attribute in the Course Info dimension to change.
The definition would use a field from Course Info and a field from Student Funding to produce the new definition.

My belief is that the new field should move from the Course Info dimension to the Student Funding dimension.

This attribute is used in lots of reports, so there is little desire from the users that I move it from one dimension to another and little desire for a new field, the users just want the definition to change.

Issues that I have got are:
How do you sort out an issue of good D/W design over strong user resistance?
Secondly how do you combine attributes from two dimensions?
What happens if an attribute over time changes from logically being in one dimension to being in another? It is not easy to shift it.

The second issue I will try and sort in the ETL but would like other ideas.

Thanks

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Re: coping with an attribute definition change

Post  ngalemmo on Mon Dec 08, 2014 12:18 pm

In dimensional modeling, as with relational modeling, the contents of a table is bound by it's key. If you have a table that is bound by course and are trying to introduce an attribute that is bound by course and student, it doesn't work. Period.

The thing is, you are not changing an attribute. You are creating a new attribute and dropping an old attribute. The users just need to accept the fact that when you add a new attribute, you need to change queries to use it.
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