One of my users has created a couple dozen categories the look like paths like so:

"/"
"/docs"
"/docs/design"
"/docs/user"
"/software"
"/software/build-system"
"/software/database"
"/software/libfoo"
"/software/libbar"

He'd liek to be able to search on, and assign, them hierarchically. How much trouble would adding a "parent category" to the category record?