Currently, having a discussion with coworkers on whether or not age is an attribute or dimension or both?
We are unable to come to an agreement on this, as age could be used as a category attribute while age could also be used as a measure to be averaged.
I am sure others have run into this, not only with age but with other fields that were on the border of attribute and measure.
How is this best handled?
Age or AgeGroup is normally its own dimension. So you would have an Age dimension that would have ages from say 1 to 150 and it would have an attribute for AgeGroup (eg 20-25).
When it comes to deciding between dimension attribute or measures, you need to meet your requirements. Sometimes you end up having something as both dimension attribute and measure in the fact table.
Read this design tip from Kimball which explains the situation with examples: