[Mondrian] Mondrian Error: Tuple contains more than one member of dimension '[Time]'

[Lajos Nagy]

Hi,

I'm new to MDX and Mondrian, so forgive my ignorance.  I'm trying to
understand mixing members from different attribute hierarchies of the same
dimension in a tuple.  At first, I thought that you could only list at most
one member from a given dimension in any tuple, but it seems not to be true:
you can list one member per *attribute hierarchy*.  OK, so I tried the
following query on the FoodMart sample database that comes packaged with the
Mondrian distro:

select [Measures].[Unit Sales] ON COLUMNS,
 ([Time].[Quarter].[Q1], [Time].[Month].[5]) ON ROWS
from [Sales]

However, this gives an error:
Mondrian Error: Tuple contains more than one member of dimension '[Time]'

Well, this would make sense in my original interpretation of the restriction
on tuples.  However, the following, semantically identical (correct me if
I'm wrong here) query executes without any complaints:

select [Measures].[Unit Sales] ON COLUMNS,
 CrossJoin({[Time].[Quarter].[Q1]}, {[Time].[Month].[5]}).Item(0) ON ROWS
from [Sales]

This seems to me an inconsistency: in both cases we construct the same tuple
on the rows axis, but the first query is rejected while the second is
accepted.

My questions are:

- Is it really an incosistency or just an apparent incosistency due to some
misunderstending of MDX semantics on my part?
- If it is an incosistency, is it a bug in the Mondrian implementation or in
the MDX specification (the former seems more likely)?

Regards,

Lajos
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