  A negotiation process by 2 agents e1 and e2 can be interleaved by another
negotiation process between, say, e1 and e3. The interleaving may alter the
resource allocation assumed at the inception of the first negotiation process.
Existing proposals for argumentation-based negotiations have focused primarily
on two-agent bilateral negotiations, but scarcely on the concurrency of
multi-agent negotiations. To fill the gap, we present a novel argumentation
theory, basing its development on abstract persuasion argumentation (which is
an abstract argumentation formalism with a dynamic relation). Incorporating
into it numerical information and a mechanism of handshakes among members of
the dynamic relation, we show that the extended theory adapts well to
concurrent multi-agent negotiations over scarce resources.
