The OVER functions are used to determine how data should be sliced, for example, relative to time periods. For more information, see OVER in Custom Expressions and Advanced Custom Expressions.
Option 
Description 
Uses all the nodes in the referenced hierarchy. This can be useful when intersecting the current node with more than one hierarchy. For example, you can show the relative sales of different product categories for each month.
Examples: Sum([Sales]) / Sum([Sales]) OVER (Intersect(All([Axis.Color]), [Axis.X])) Sum([Sales]) / Sum([Sales]) OVER (All([Axis.X])) * 100 

Uses all nodes, including the current, to the end of the level.
Example: Sum([Sales]) OVER (AllNext([Axis.X])) 

Uses all nodes, including the current, from the start of the level. This can be used to calculate the cumulative sum.
Examples: Sum([Sales]) OVER (AllPrevious([Axis.X])) Sum([Sales]) OVER (Intersect(Parent([Axis.X]), AllPrevious([Axis.X]))) 

Selects the first node on the current level.
Example: Sum([Sales])  Sum([Sales]) OVER (FirstNode([Axis.X])) 

Returns the intersected rows from nodes in different hierarchies. See also AllPrevious and All.
Example: Intersect(Parent([Axis.X]), All([Axis.Color]), Parent([Axis.Rows]), ...) 

Selects the last node on the current level.
Example: Sum([Sales])  Sum([Sales]) OVER (LastNode([Axis.X])) 

Includes the current node and the n  1 previous nodes. This can be used to calculate moving averages.
Example: Sum([Sales]) OVER (LastPeriods(3, [Axis.X]))/3 

Allows you to specify your own node navigation. The method has four arguments: Arg1 is the hierarchy to navigate. Arg2 is a string value specifying the level in the hierarchy that you should navigate up to. Arg3 is an integer specifying the number of steps to move sideways in the hierarchy at the level specified by Arg1. Arg4 is optional and determines the level in the hierarchy to move down to. This argument can be omitted in which case a navigation to the leaf level is made. Examples: Sum([Sales]) OVER NavigatePeriod([Axis.X], “Year”, 1) Sum([Value]) OVER NavigatePeriod([Axis.X], “Year”, 0, 0) Sum([Sales]) OVER NavigatePeriod([Axis.X], 2, 1, 2) 

Compares the current node with the next node on the same level in the hierarchy. If there is no next node, that is, if the current node is the last node for the current level, the resulting subset will not contain any rows.
Example: Sum([Sales])  Sum([Sales]) OVER (Next([Axis.X])) 

Uses the next node which has the next value on the same level as the current node. If there is no next node, that is, if the current node is the last node for the current level, the resulting subset will not contain any rows.
Example: Sum([Sales]) OVER (NextPeriod([Axis.X])) 

Uses the previous parallel node with the same value on the same level as the current node. For example, this can be used to compare sales results for each month with the corresponding months the previous year.
Example: Sum([Sales])Sum([Sales]) OVER (ParallelPeriod([Axis.X])) 

Uses the parent subset of the current node. If the node does not have a parent, all rows are used as the subset.
Examples: Sum([Sales]) / Sum([Sales]) OVER (Parent([Axis.Color])) Sum([Sales]) / Sum([Sales]) OVER (Parent([Axis.X])) * 100 

Uses the previous node on the same level as the current node to compare the result of the current node with the previous one. If there is no previous node, that is, if the current node is the first node for the current level, the resulting subset will not contain any rows.
Example: Sum([Sales])  Sum([Sales]) OVER (Previous([Axis.X])) 

Uses the previous node which has the previous value on the same level as the current node. If there is no previous node, that is, if the current node is the first node for the current level, the resulting subset will not contain any rows.
Example: Sum([Sales]) OVER (PreviousPeriod([Axis.X])) 
See also: