IgnoreUnrelatedDimensions is a property of Measure Groups. By default its value is TRUE. So what does that mean? A Measure Group need not be linked to all available Dimensions in the cube. In other words there are some Dimensions that are unrelated to a Measure Group. When IgnoreUnrelatedDimensions property is TRUE, the Measure Group ignores any dimension not linked to it by showing the current value for all members in the unrelated dimension. This is confusing to the Information Consumer when the cube is browsed.
Take for example, the AdventureWorks cube. The Sales Quotas measure group is related to Employee Dimension and unrelated to Product Dimension as shown in Figure 1
With the default value IgnoreUnrelatedDimensions=TRUE, the cube when sliced by Employee (Related Dimension) and Product (Unrelated Dimension), the result is confusing to the Information Consumer as shown in Figure 2
To avoid this confusion, set IgnoreUnrelatedDimensions=FALSE. From BIDS, Open the cube. Go to Dimension Linkage tab, right click on the Measure Group and set this property as shown below in Figure 3.
By doing so, Analysis Services return a blank value for Dimensions that are unrelated, as shown below in Figure 4.
Personally, I would prefer the default value of IgnoreUnrelatedDimenisons to be FALSE. I haven’t found any compelling reason for this property to have a default value of TRUE. At least there is a workaround!