It would be a great comfort features, beaing able to rebuild the history/trends of a depending item, based on the existing data of the parent item.

 

Example:

I am saving raw webpage content (source code) for analysis and therfore parsing it with dependent items for getting the informations needed.

It would be great to create a dependent item later on and being able to rebuild its parsed data based on the already available data of its parent item. This would be great for data analysis.