You may or may not be aware of the property mondrian.olap.SsasCompatibleNaming. It controls the naming of elements, in particular how Mondrian names hierarchies when there are multiple hierarchies in the same dimension.
Let's suppose that there is a dimension called 'Time', and it contains hierarchies called 'Time' and 'Weekly'.
If SsasCompatibleNaming is false, the dimension and the first hierarchy will both be called '[Time]', and the other hierarchy will be called '[Time.Weekly]'.
If SsasCompatibleNaming is true, the dimension will be called '[Time]', the first hierarchy be called '[Time].[Time]', and the other hierarchy will be called '[Time].[Weekly]'.
As you can see, SsasCompatibleNaming makes life simpler, if slightly more verbose, because it gives each element a distinct name. There are knock-on effects, beyond the naming of hierarchies. The most subtle and confusing effect is in the naming of levels when the dimension, hierarchy and level all have the same name. If SsasCompatibleNaming is false, then [Gender].[Gender].Members is asking for the members of the gender level, and yields two members. If SsasCompatibleNaming is true, then [Gender].[Gender].Members is asking for the members of the gender hierarchy, and yields three members (all, F and M).
Usually, however, Mondrian is forgiving in how it resolves names, and if elements have different names, it will usually find the element you intend.
The default value is false. However, that leads to naming behavior which is not compatible with other MDX implementations, in particular Microsoft SQL Server Analysis Services (versions 2005 and later).
From mondrian-4 onwards, the property will be set to true. (You won't be able to set it to false.) This makes sense, because in mondrian-4, with attribute-hierarchies, there will typically be several hierarchies in each dimension. We will really need to get our naming straight.
What do we recommend? If you are using Pentaho Analyzer, Saiku or JPivot today, we recommend that you use the default value, false. But if you are writing your own MDX (or have built your own client), try setting the value to true. The new naming convention actually makes more sense, and moving to it now will minimize the disruption when you move to mondrian-4.
I am just about to check in a change that uses a new, and better name resolution algorithm. It will be more forgiving, and standards-compliant, in how it resolves the names of calculated members. However, it might break compatibility, so it will only be enabled if SsasCompatibleNaming is true.
Are you using this property today? Let us know how it's working for you.