|Alfred North Whitehead|
My initial thought that generation, creativity, temporalism and change ("process") happens to be more significant for Whitehead than a theory of relations as such (i.e. "relationism") can be found HERE. Of course, process and actual occasions ("instants") go hand-in-hand.
While this is on my mind, and this is just a passing thought: I am reminded of Peirce here. In a categorial scheme Secondness (reaction and relation) and Thirdness (the habits of created instants) both depend upon the generativity of creative Firstness (the can-be possible, i.e. deep hyperchaotic Potenzen). Relations and habits could not be if it weren't for Firsts. Whitehead, following Peirce here, goes on to essentialize the modal aspect of Firstness into his "eternal objects" - which are indeed timeless - but which are also nonetheless active and generative objects-as-powers (forms of objects, really). Now for Hartshorne, on the other hand, these eternal objects do not "exist" until they are created. The pre-actual items of the universe are not and in being-not possess a virtual power (ala Meillassoux).
In conclusion, it is simply wrong-headed to call Whitehead a "relationist" without emphasizing some features of this thought which seem to balance or temper the relational aspect of his work, e.g. his temporalism, his theory of modes vis-a-vis eternal objects, the doctrine of contributionism, or in general taking account of what dynamic singular agents do versus how they simply "relate." This all involves a processive account of the universe which goes beyond a simple relational philosophy. Change (temporalism) and generativity (creativity) are at the core of Whithead's thought, not just an account of relations.