how to determine which date hierarchy a user is drilling through - ssas

Question

I am trying to implement a calculation dimension along the lines of the DateTool mechanism as outlined in the Expert Cube Development book by Chris Webb et al.
The issue is that, like most organizations, we have the need to report by both fiscal and calendar hierarchies, and based on multiple dates in our transaction table.
I would dearly love to be able to define one calculation dimension which redefines which time dimension and which calendar it uses based on which time dimension and hierarchy the user has chosen.
Here is a sample bit of code:
( [Time Calculations].[Calculation].[Year to Date] )
=
Sum(PeriodsToDate([Time Order Date].[Fiscal Date].[Fiscal Year Name],
[Time Order Date].[Fiscal Date].CurrentMember
),
[Time Calculations].DefaultMember
)
I would very much like to rewrite this as:
( [Time Calculations].[Calculation].[Year to Date] )
=
case
when user is viewing using the Order Date, Fiscal Calendar then
Sum(PeriodsToDate([Time Order Date].[Fiscal Date].[Fiscal Year Name],
[Time Order Date].[Fiscal Date].CurrentMember
),
[Time Calculations].DefaultMember
)
when user is viewing using the Ship Date, Fiscal Calendar then
Sum(PeriodsToDate([Time Ship Date].[Fiscal Date].[Fiscal Year Name],
[Time Ship Date].[Fiscal Date].CurrentMember
),
[Time Calculations].DefaultMember
)
when user is viewing using the Order Date, Calendar hierarchy then
Sum(PeriodsToDate([Time Order Date].[Calendar].[Year Name],
[Time Order Date].[Date].CurrentMember
),
[Time Calculations].DefaultMember
)
when user is viewing using the Ship Date, Calendar hierarchy then
Sum(PeriodsToDate([Time Ship Date].[Date].[Year Name],
[Time Ship Date].[Date].CurrentMember
),
[Time Calculations].DefaultMember
)
else null end
Is this possible?

Answer 1

You could try to insert following into your cube script. This should be aware of any Year levels no matter whether they are used on an axis or in a subselect.
This code uses the fact that dynamic sets are aware of subselects. In addition to that the keyword Existing is used in the IIF so that the calculation also knows about the hierarchies used in the WHERE clause or an Axis.
The Head function is there for performance reasons. You just need to know if at least 1 member of the dimensions is selected. There is no need to count all of them.
The script returns NULL when none of the required hierarchies are selected.
CREATE HIDDEN DYNAMIC SET CURRENTCUBE.[OrderDateFiscalYearAll]
AS [Time Order Date].[Fiscal Date].[Fiscal Year Name].MEMBERS;
CREATE HIDDEN DYNAMIC SET CURRENTCUBE.[OrderDateCalendarYearAll]
AS [Time Order Date].[Calendar].[Year Name].MEMBERS;
CREATE HIDDEN DYNAMIC SET CURRENTCUBE.[ShipDateFiscalYearAll]
AS [Time Ship Date].[Fiscal Date].[Fiscal Year Name].MEMBERS;
CREATE HIDDEN DYNAMIC SET CURRENTCUBE.[ShipDateCalendarYearAll]
AS [Time Ship Date].[Calendar].[Year Name].MEMBERS;
Scope([Time Calculations].[Calculation].[Year to Date]);
This = IIF(Count(Head(Existing [OrderDateFiscalYearAll], 1)) > 0
,/* Insert OrderDateFiscalYear calculation here */
,IIF(Count(Head(Existing [OrderDateCalendarYearAll], 1)) > 0
,/* Insert OrderDateCalendarYear calculation here */
,IIF(Count(Head(Existing [ShipDateFiscalYearAll], 1)) > 0
,/* Insert ShipDateFiscalYear calculation here */
,IIF(Count(Head(Existing [ShipDateCalendarYearAll], 1)) > 0
,/* Insert ShipDateCalendarYear calculation here */
,NULL))))
End Scope;