Very Customed Aggregation
I started a long conversation about this subject in the MDSN SSAS forum. I think that it's a question and a principal that every advanced MDX programmer should be familiar with.
It all started with a customer that needed a standard deviation aggregation. I thought that it would be simple because there's a StdDev function in MDX, but it turned out that my customer had major plans for me: He wanted this aggregation to act for every dimension he puts on his axis. This means that the aggregation is not defined over a specific dimension (such as date), but the std-dev is defined over the current dimension in the axis.
Tags: mdx, aggregation