I have a node display for more than one product variation. Normally the user has to select one of the variation options by selecting them from the drop-down list which rebuilds the node display via AJAX.
Now say for instance that I want to link one of the product variations from else where. If I simply link www.example.com/node/10 the default product variation will be displayed which might not be the one I would like to present to the user.
So I probably have to send a query parameter in the URL, for example www.example.com/node/10?product_id=15, and trigger the AJAX event programmatically in my custom module.