Abstract We propose a general framework for modelling and formal reasoning about multi-agent systems and, in particular, multi-stage games where both quantitative and qualitative objectives and constraints are involved. Our models enrich concurrent game models with payoffs and guards on actions associated with each state of the model and propose a quantitative extension of the logic $${\textsf {ATL}}^{*}$$ ATL ∗ that enables the combination of quantitative and qualitative reasoning. We illustrate the framework with some detailed examples. Finally, we consider the model-checking problems arising in our framework and establish some general undecidability and decidability results for them.

In alternating-time temporal logic ATL*, agents with perfect recall assign choices to sequences of states, i.e., to possible finite histories of the game. However, when a nested strategic modality is interpreted, the new strategy does not take into account the previous sequence of events. It is as if agents collect their observations in the nested game again from scratch, thus, effectively forgetting what they observed before. Intuitively, it does not fit the assumption of agents having perfect recall of the past. In this article, we investigate the alternative semantics for ATL*where the past is not forgotten in nested games. We show that the standard semantics of ATL*coincides with the “truly perfect recall” semantics for agents with perfect information and in case of so-called “objective” abilities under uncertainty. On the other hand, the two semantics differ significantly for the most popular (“subjective”) notion of ability under imperfect information. The same applies to the standard vs. “truly perfect recall” semantics of ATL*with persistent strategies. We compare the relevant variants of ATL*by looking at their expressive power, sets of validities, and tractability of model checking.

International audience

Alternating Time Temporal Logic (ATL) is widely used for the verification of multi-agent systems. We consider Resource Agent Logic ( RAL ), which extends ATL to allow the verification of properties of systems where agents act under resource constraints. The model checking problem for RAL with unbounded production and consumption of resources is known to be undecidable. We review existing (un)decidability results for fragments of RAL , tighten some existing undecidability results, and identify several aspects which affect decidability of model checking. One of these aspects is the availability of a ‘do nothing’, or idle action, which does not produce or consume resources. Analysis of undecidability results allows us to identify a significant new fragment of RAL for which model checking is decidable.

We propose a new strategic model of negotiation, called Boolean negotiation games. Our model is inspired by Boolean games and the alternating offers model of bargaining. It offers a computationally grounded model for studying properties of negotiation protocols in a qualitative setting. Boolean negotiation games can yield agreements that are more beneficial than stable solutions (Nash equilibria) of the underlying Boolean game.

This paper focuses on computational mechanisms that control the behavior of autonomous systems at runtime without necessarily restricting their autonomy. We build on existing approaches from runtime verification, control automata, and norm-based systems, and define norm-based controllers that enforce norms by modifying system behavior at runtime to make it norm compliant. For many applications, an autonomous system should comply with a set of norms. We extend our approach to a distributed setting, where a set of norm-based controllers jointly modify the runtime behavior of an autonomous system. The norms that a set of norm-based controllers jointly enforce are investigated and characterized in terms of the norms that are enforced by individual norm-based controllers. We show that a set of norm-based controllers is able to modify the runtime behavior of an autonomous system to make it compliant with all norms that the individual norm-based controllers aim at enforcing.

Mobile ad hoc networks are networks that allow (mobile) users to communicate in heterogeneous environments without relying on a fixed infrastructure, examples of which are mobile communication in large urban spaces or in public transportation. Due to their many advantages, such as decentralization, independence of communication infrastructure, flexibility etc., their field of use steadily increases. However, networks of this kind also raise new problems related to, for example, routing and data delivery, security and privacy, trust and usability. In this article, we propose a formal model of mobile ad hoc networks and address questions regarding optimal and stable network topologies. In particular, stability is important to ensure that communication is reliable and that applications designed for such networks are accepted by the users. We analyse stability from a game theoretic point of view, and propose a non-cooperative as well as a cooperative modelling. Moreover, we allow users to express constraints on how their communication should be handled in the network in order to ensure user constraints, e.g. related to privacy and security. For this purpose we use the temporal logic CTL. Finally, we analyse the complexity of associated verification and synthesis problems regarding optimal/stable network topologies.

In alternating-time temporal logic ATL*, agents with perfect recall assign choices to sequences of states, i.e., to possible finite histories of the game. However, when a nested strategic modality is interpreted, the new strategy does not take into account the previous sequence of events. It is as if agents collect their observations in the nested game again from scratch, thus effectively forgetting what they observed before. Intuitively, it does not fit the assumption of agents having perfect recall of the past.

Alternating-time temporal logic (ATL) is a wellknown logic for reasoning about strategic abilities of agents. An important feature that distinguishes variants of ATL for imperfect information scenarios is that the standard fixed point characterizations of temporal modalities do not hold anymore. In this paper, we show that adding explicit fixed point operators to the “next-time ” fragment of ATL already allows to capture abilities that could not be expressed in ATL. We also illustrate that the new language allows to specify important kinds of abilities, namely ones where the agents can always recompute their strategy while executing it. Thus, the agents are not assumed to remember their strategy by definition, like in the existing variants of ATL. Last but not least, we show that verification of such abilities can be cheaper than for all the variants of “ATL with imperfect information ” considered so far. 1

The verification and modelling of multi-agent systems is an important topic that has attracted much attention in recent years. Resources, however, have only recently been studied as simple extensions to well-known logics. Trying to find a set of useful features while retaining essential properties for practical use, we explore the question: Where are the limits of what can be verified about resource-bounded agents? We try to answer this question by considering several natural logic-based settings that may arise and prove that verification is usually undecidable apart from bounded or otherwise restrictive settings. Most interestingly, we identify various factors that influence the (un-)decidability and provide grounds for future research on more promising constraints leading to decidable fragments.

Alternating-time Temporal Logic (ATL) is probably themost influential logic of strategic ability that has emerged in recent years. The idea of ATL is centered around cooperation modalities: ≪A≫γ is satisfied if the group A of agents has a collective strategy to enforce temporal property γ against the worst possible response from the other agents. So, the semantics of ATL shares the "all-or-nothing" attitude of many logical approaches to computation. Such an assumption seems appropriate in some application areas (life-critical systems, security protocols, expensive ventures like space missions). In many cases, however, one might be satisfied if the goal is achieved with reasonable likelihood. In this paper, we try to soften the rigorous notion of success that underpins ATL.