I am massively excited about the new Connected Data Sources functionality as part of Spring 17. This has been a major issue for end users who didnt want to jump into the code but had multiple datasets they needed to join together as part of the dashboard previously.
The new Connected Data Sources, although not as powerful as the selection bindings... is a lot easier to implement. It is a declarative interface where you can select a column from multiple datasources where same values are in each.
An example of this maybe country states or city's across 2 datasets that you may want to filter on both sets.
Below is a video taking you through this
Now that I have shared the video - below is the code that is now part of the dashboard to identify the rules and the dimensions that are now doing the faceting... below that is a copy of the total dashboard JSON so you can see the code from the video.
As you can see above , we are defining the below for each of the Data Source Connections: