[Mondrian] Same dimension in different axis
Pedro Alves
pedro at neraka.no-ip.org
Thu Jul 16 19:13:38 EDT 2009
This is *great* news, and will affect a lot of the development that we'll
do tomorrow.
The cdf team (cdf == community dashboard framework, a project that allows
an easy way to build dashboards in pentaho) is working on a cdf editor that
will be very closely connected to mondrian, and the engine will generate
selector, charts, tables, etc, while the user only has to drag and drop
dimensions / levels in a GUI.
When will this be available? I don't mind working with a build from source
or even try to implement this myself. Am I being too naive to think that
all I need is to go to the block that checks if a member is used in more
than one dimension and comment that out? :)
ps: I remember a while back Julian twitting about the possibility to use
sets in the where clause. How is the syntax? I tried it recently and still
got an error. This would be great to avoid an extra member definition with
just an aggregate();
-pedro
On Thu, Jul 16, 2009 at 12:48:17PM -0700, Julian Hyde wrote:
> I agree. This has been on our backlog for some time. Matt Campbell has
> been pushing for it in particular. It didn't quite make the cut for 3.1.
> Inexplicably there was no issue logged for it -- at least, I couldn't find
> one -- so I logged [1]http://jira.pentaho.com/browse/MONDRIAN-578.
>
> If we do this, there's no reason why people shouldn't start using
> 'attribute hierarchies'. Attribute hierarchies are more of a schema design
> style than a feature. The result is that hierarchies are clustered into a
> small number of dimensions. For example, [Gender] and [Marital Status]
> would both become hierarchies within the [Customer] dimension.
>
> We did half of the work for 3.1: cleaning up how mondrian resolves
> members, levels and hierarchies when there are multiple hierarchies, and
> making it consistent with SSAS 2005. Without that work, using attribute
> hierarchies would have been tricky.
>
> This will be in the next release of mondrian.
>
> Julian
>
> --------------------------------------------------------------------------
>
> From: mondrian-bounces at pentaho.org [mailto:mondrian-bounces at pentaho.org]
> On Behalf Of Brian Vandenberg
> Sent: Thursday, July 16, 2009 8:20 AM
> To: Mondrian developer mailing list; Pedro Alves
> Subject: Re: [Mondrian] Same dimension in different axis
> I agree with Pedro on this, even with using the same dimension on
> rows/columns. If I want information broken out by month & day of week,
> as it stands I'd have to settle for one of:
>
> * Break it out on one axis and live with it -- while I can't easily see
> relationships between events that occur on mondays every month, there's
> not much I can do about it otherwise.
> * Create either a mirrored date dimension or a day of week dimension
> ** The mirrored date dimension could easily create confusion with
> users. There's that saying "keep it simple, stupid". More dimensions =
> more complexity.
> ** The day of week dimension would suffice, but has some problems:
> *** requires yet another dimension key on my fact table. If my fact
> table has many dimensions, more than one of which I'd like to use at
> different levels of aggregation on different axes, this bloats the fact
> table
> *** I would probably have to remove day of week from the date dimension,
> which might be annoying under other circumstances where I want the date
> dimension to have both month & day of week. The date dimension can have
> multiple drill-down paths, but that also creates more options for users
> -- and users don't like too many options
> * Just break it out on one axis, then write custom code to iterate over
> the query results in a different sequence than presented
>
> For whatever reason, it's easier for people to wrap their heads around
> few columns with many rows, than many rows and fewer columns.
> Additionally, it'd be easier to see trends or patterns by applying the
> day of week on a different axis from the month.
>
> While it's true a report or visualization would be _capable_ of
> presenting the information in whatever way it sees fit, it'd be nice for
> the [report/visualization] developer, and for those tech savvy users
> with just enough knowledge to design simple queries.
>
> I see this as code re-use. Why create 5 dimensions to represent the
> same concept in different ways when one dimension would suffice if you
> have more flexibility in its use.
>
> -Brian
>
> On Thu, Jul 16, 2009 at 4:06 AM, Pedro Alves <[2]pedro at neraka.no-ip.org>
> wrote:
>
> Hey there.
>
> Is there a way to remove the restriction of not having the same
> dimension
> in more than one axis?
>
> I'm working on a dashboard generator that dynamically integrates with
> mondrian, but this is a very bad restriction if I want users to apply
> whatever filters they want. The following query is an example of the
> type
> of stuff I'd love to be able to do:
>
> select
> Descendants([Products], [Products].[Version]) on rows,
> Measures.[Downloads] on columns
> >From ...
> where
> ([Dates].[Date].[2009-07-16],
> [Products].[Firefox].[3.5],
> [Download Types].[Complete])
>
> Instead, I need to do
>
> select
> Descendants([Products].[Firefox].[3.5], [Products].[Version]) on
> rows,
> Measures.[Downloads] on columns
> >From ...
> where
> ([Dates].[Date].[2009-07-16],
> [Download Types].[Complete])
>
> In terms of plain queries this is not complicated; But in a scenario
> where
> the users is free to choose whatever dimensions he wants to chart
> against
> whatever conditions he wants to filter, my algorithm to generate the
> query
> gets much more complicated than I'd like
>
> And I don't think there's a reason for this restriction; There were
> projects where I've defined in the mondrian schema the same dimension
> duplicated just to be able to do what I need. Another example is here:
> [3]http://tinyurl.com/kk9b2b . Having to define a [Time2] dimension
> that's
> absolutely identical to [Time] to obtain a very standard crosstab
> information.
>
> Any tips appreciated
>
> -pedro
>
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>
> References
>
> Visible links
> 1. http://jira.pentaho.com/browse/MONDRIAN-578
> 2. mailto:pedro at neraka.no-ip.org
> 3. http://tinyurl.com/kk9b2b
> 4. mailto:Mondrian at pentaho.org
> 5. http://lists.pentaho.org/mailman/listinfo/mondrian
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--
Pedro Alves
pmgalves-at-gmail.com
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