A synonym to of which and likewise an inanimate alternative to whose, the possessive of who. Whereas "whose" is defined to be the possessive of both "who" and "which", there is a hesitation to use "whose" with an inanimate antecedent, and so the word "which's" is beginning to be used instead.
"If the previous request (which's response was generated by the jsp) set a cookie on the client"
"A game for all four contestants, one of which reviews a film, which's title is selected by the audience. The other three act out the film described by the reviewer."