IBIS (Issue Based Information System) provides a widely
adopted approach for knowledge representation especially
suitable for the challenging task of representing wicked decision
problems. While many tools for visualisation and collaborative
development of IBIS graphs are available, automated
decision support in this context is still underdeveloped, even
though it would benefit several applications. QuAD (Quantitative
Argumentation Debate) frameworks are a recently proposed
IBIS-based formalism encompassing automated decision
support by means of an algorithm for quantifying the
strength of alternative decision options, based on aggregation
of the strength of their attacking and supporting arguments.
The initially proposed aggregation method, however, may
give rise to discontinuities. In this paper we propose a novel,
discontinuity-free algorithm for computing the strength of decision
options in QuAD frameworks. We prove that this algorithm
features several desirable properties and we compare
the two aggregation methods, showing that both may be appropriate
in the context of different application scenarios.