You can find videos of the invited talks on youtube. The links are found next to the talk titles.

#### Guillermo Perez (University of Antwerp, Belgium)

**Regret Minimization in Discounted-Sum Games** [video]

Discounted-sum games provide a formal model for the study of reinforcement learning, where the agent is enticed to get rewards early since later rewards are discounted. When the agent interacts with the environment, she may realize that, with hindsight, she could have increased her reward by playing differently: this difference in outcomes constitutes her regret value. The agent may thus elect to follow a regret- minimal strategy. In this talk, we will see that (1) there always exist regret-minimal strategies that are admissible—a strategy being inadmissible if there is another strategy that always performs better; (2) computing the minimum possible regret or checking that a strategy is regret-minimal can be done in coNP with an NP oracle, disregarding the computational cost of numerical analysis (otherwise, this bound becomes PSPACE). Finally, we will give a brief overview of other related problems that we have studied and some interesting problems that remain open.

#### Adnan Darwiche (UCLA, USA)

**Three Modern Roles for Logic in AI** [video]

I will discuss three modern roles for logic in artificial intelligence, which are based on the theory of tractable Boolean circuits: (1) logic as a basis for computation, (2) logic for learning from a combination of data and knowledge, and (3) logic for reasoning about the behavior of machine learning systems.

#### Erika Ábrahám (RWTH Aachen University, Germany)

**Probabilistic Hyperproperties** [video]

Four decades ago, Lamport used the notion of trace properties as a means to specify the correctness of individual executions of concurrent programs. This notion was later formalized and classified by Alpern and Schneider to safety and liveness properties. Temporal logics like LTL and CTL were built based on these efforts to give formal syntax and semantics to requirements of trace properties. Subsequently, verification algorithms were developed to reason about individual executions of a system.

However, it turns out that many interesting requirements are not trace properties. For example, important information-flow security policies (e.g. noninterference, observational determinism) or service level agreements (e.g. mean response time, percentage uptime) cannot be expressed as properties of individual execution traces of a system. Rather, they are properties of sets of execution traces, also known as hyperproperties. Temporal logics such as HyperLTL and HyperCTL∗ have been proposed to provide a unifying framework to express and reason about hyperproperties.

This talk is devoted to special class of hyperproperties: we ask the question what are hyperproperties in the context of systems with random behavior. We will discuss what are relevant probabilistic relations between independent executions of a system, how we can formally express them in a temporal logic, and how we can decide the truth of such statements.

#### Jan Křetínský (TU München, Germany)

**Approximating Values of Generalized-Reachability Stochastic Games +
Automata Tutor** [video]

Simple stochastic games are turn-based two-and-a-half-player games with a reachability objective. The basic question asks whether one player can ensure reaching a given target with at least a given probability. A natural extension is games with a conjunction of such conditions as objective. Despite a plethora of recent results on the analysis of systems with multiple objectives, the decidability of this basic problem remains open. Here we present an algorithm approximating the Pareto frontier of the achievable values to a given precision. Moreover, it is an anytime algorithm, meaning it can be stopped at any time returning the current approximation and its error bound.

After the talk, we present a short demo of Automata Tutor, a tool for teaching automata theory, which could be helpful to many GandALF participants.