Bridging Commonsense Reasoning and Probabilistic Planning via a Probabilistic Action Language

To be responsive to dynamically changing real-world environments, an intelligent agent needs to perform complex sequential decision-making tasks that are often guided by commonsense knowledge. The previous work on this line of research led to the framework called interleaved commonsense reasoning and probabilistic planning (icorpp), which used P-log for representing commmonsense knowledge and Markov Decision Processes (MDPs) or Partially Observable MDPs (POMDPs) for planning under uncertainty. A main limitation of icorpp is that its implementation requires non-trivial engineering efforts to bridge the commonsense reasoning and probabilistic planning formalisms. In this paper, we present a unified framework to integrate icorpp’s reasoning and planning components. In particular, we extend probabilistic action language pBC+ to express utility, belief states, and observation as in POMDP models. Inheriting the advantages of action languages, the new action language provides an elaboration tolerant representation of POMDP that reflects commonsense knowledge. The idea led to the design of the system pbcplus2pomdp, which compiles a pBC+ action description into a POMDP model that can be directly processed by off-the-shelf POMDP solvers to compute an optimal policy of the pBC+ action description. Our experiments show that it retains the advantages of icorpp while avoiding the manual efforts in bridging the commonsense reasoner and the probabilistic planner.

Representing hybrid automata by action language modulo theories

Both hybrid automata and action languages are formalisms for describing the evolution of dynamic systems. This paper establishes a formal relationship between them. We show how to succinctly represent hybrid automata in an action language which in turn is defined as a high-level notation for answer set programming modulo theories—an extension of answer set programs to the first-order level similar to the way satisfiability modulo theories (SMT) extends propositional satisfiability (SAT). We first show how to represent linear hybrid automata with convex invariants by an action language modulo theories. A further translation into SMT allows for computing them using SMT solvers that support arithmetic over reals. Next, we extend the representation to the general class of non-linear hybrid automata allowing even non-convex invariants. We represent them by an action language modulo ordinary differential equations, which can be compiled into satisfiability modulo ordinary differential equations. We present a prototype systemcplus2aspmtbased on these translations, which allows for a succinct representation of hybrid transition systems that can be computed effectively by the state-of-the-art SMT solverdReal.

The public action languages approach to public affairs

<p><em>Este artigo parte da observação feita por autores envolvidos com diferentes aspectos das ações públicas, uma vez que o Estado não é sinônimo de assuntos públicos. Do ponto de vista policêntrico, no qual o público ou públicos são atores-chave e independentes, questiona-se o papel central que a política pública supostamente assumiu na articulação da discussão e provisão de bens e serviços públicos. O artigo adota uma perspectiva histórica da emergência da política pública na língua inglesa em diferentes momentos e focaliza três períodos reconhecidos como aqueles nos quais as democracias anglófonas deram passos significativos para a ampliação da agenda de debate dos assuntos públicos: o New Deal de Roosevelt, 1933; o Governo do Partido Trabalhista britânico, 1945, e as administrações Johnson (1963-1968). Em todos esses casos, houve inovações muito práticas no tratamento de questões muito difíceis, mas com muito pouca – se houve – discussão de política pública. Considerando que fala e ação andam juntas, quais outras linguagens sociais (para usar o termo de Bakhtin, 1986) estavam disponíveis? Ao apontar que elas eram muitas, das quais a maior parte continua presente e bastante ativa hoje, o artigo questiona a centralidade e inevitabilidade da política pública e propõe abordar linguagens de ação pública para o estudo dos assuntos públicos. </em></p>