In the Performance Point Server 2007 Dashboard Designer, you create a data source using either a standard connection or with a connection string. I use the connection string option myself, but I never remember the syntax of the connection string (to a AS cube).
So here how’s I get the connection string:
Open excel (I use 2007)
Go to the data tab
From Other sources
From Analysis Services
Put in your server name (I leave the default for Log on credentials)
Then choose what cube you want (if you have more than one cube)
Click Finish (if you already have a data source of that name already existing, then you will have a pop up asking if you want to continue, I choose yes)
Click on the Definition Tab
Viola, there is the connection string to your cube.
Now you can copy and paste that back into Dashboard Designer.