Rbosaghz writeup of shortest path dependency kernel

This is a review of Bunescu_2005_a_shortest_path_dependency_kernel_for_relation_extraction by user:Rbosaghz.

This is another example of how kernels can be used to aid learning. In this case, the task is relation extraction, and the kernel is defined by the shortest path between the two named entities in the dependency graph. What bothers me about this work is that it's not immediately clear (to me) how this kernel is guaranteed to be a valid kernel. It probably is, but I don't see a proof or explanation.