The ability to publish data extracts for common use is great. In some cases, the published data set actually is best used as a join condition to other data.
For example, if you have a customer file that is, hopefully, very large, you might want to join this to sales data or shipping data.
Currently, you can't use more than one published extract in a single dataset. When I choose an extract, a list of the data sources is provided to use in your workbook. I would like to see the interface allow me to drag published extracts onto the data pane in the same way I can drag tables from a relational data source. I could then join two or more together.