Abstract. In the traditional Boolean setting of formal verification, alternating automata are the key to many algorithms and tools. In this setting, the correspondence between disjunctions/conjunctions in the specification and nondeterministic/universal transitions in the automaton for the specification is straightforward. A recent exciting research direction aims at adding a quality measure to the satisfaction of specifications of reactive systems. The corresponding automata-theoretic framework is based on weighted automata, which map input words to numerical values. In the weighted setting, nondeterminism has a minimum semantics – the weight that an automaton assigns to a word is the cost of the cheapest run on it. For universal branches, researchers have studied a (dual) maximum semantics. We argue that a summation semantics is of interest too, as it captures the intuition that one has to pay for the cost of all conjuncts. We introduce and study alternating weighted automata o...