Know how to conduct the operational, discussion part of a negotiation.
A negotiation should start from a place where all potential conflicts are addressed. There is no point in leaving out issues of conflict, these may prevent resolution of the negotiation. Contribution to the negotiation should be carefully considered and well constructed. Contributions from other parties should be listened to attentively and analysed within the context of the negotiation as a whole and within the context of the positions of each negotiation party.
The knowledge named 'Conduct a negotiation' is considered to be quite critical.
In addition, the knowledge is thought to be rather complex and difficult to learn, it is almost always learned from experience, and is specialised knowledge.
Opinion is that it is minimally justifiable knowledge.