Fiora Pirri

Some contributions to the metatheory of the situation calculus

We focus on a rich axiomatization for actions in the situation calculus that includes, among other features, a solution to the frame problem for deterministic actions. Our work is foundational in nature, directed at simplifying the entailment problem for these axioms. Specifically, we make four contributions to the metatheory of situation calculus axiomatizations of dynamical systems: (1) We prove that the above-mentioned axiomatization for actions has a relative satisfiability property; the full axiomatization is satisfiable iff the axioms for the initial state are. (2)We define the concept of regression relative to these axioms, and prove a soundness and completeness theorem for a regression-based approach to the entailment problem for a wide class of queries. (3) Our formalization of the situation calculus requires certain foundational axioms specifying the domain of situations. These include an induction axiom, whose presence complicates human and automated reasoning in the situation calculus. We characterize various classes of sentences whose proofs do not require induction, and in some cases, some of the other foundational axioms. (4)We prove that the logic programming language GOLOG never requires any of the foundational axioms for the evaluation of programs.

Experience in System Design for Human-Robot Teaming in Urban Search and Rescue

The paper describes experience with applying a user-centric design methodology in developing systems for human-robot teaming in Urban Search & Rescue. A human-robot team consists of several robots (rovers/UGVs, microcopter/UAVs), several humans at an off-site command post (mission commander, UGV operators) and one on-site human (UAV operator). This system has been developed in close cooperation with several rescue organizations, and has been deployed in a real-life tunnel accident use case. The human-robot team jointly explores an accident site, communicating using a multi-modal team interface, and spoken dialogue. The paper describes the development of this complex socio-technical system per se, as well as recent experience in evaluating the performance of this system.

Rescue robots at earthquake-hit Mirandola, Italy: A field report

In May 2012, two major earthquakes occurred in the Emilia-Romagna region, Northern Italy, followed by further aftershocks and earthquakes in June 2012. This sequence of earthquakes and shocks caused multiple casualties, and widespread damage to numerous historical buildings in the region. The Italian National Fire Corps deployed disaster response and recovery of people and buildings. In June 2012, they requested the aid of the EU-funded project NIFTi, to assess damage to historical buildings, and cultural artifacts located therein. To this end, NIFTi deployed a team of humans and robots (UGV, UAV) in the red-area of Mirandola, Emilia-Romagna, from Tuesday July 24 until Friday July 27, 2012. The team worked closely together with the members of the Italian National Fire Corps involved in the red area. This paper describes the deployment, and experience.

A general method for the point of regard estimation in 3D space

A novel approach to 3D gaze estimation for wearable multi-camera devices is proposed and its effectiveness is demonstrated both theoretically and empirically. The proposed approach, firmly grounded on the geometry of the multiple views, introduces a calibration procedure that is efficient, accurate, highly innovative but also practical and easy. Thus, it can run online with little intervention from the user. The overall gaze estimation model is general, as no particular complex model of the human eye is assumed in this work. This is made possible by a novel approach, that can be sketched as follows: each eye is imaged by a camera; two conics are fitted to the imaged pupils and a calibration sequence, consisting in the subject gazing a known 3D point, while moving his/her head, provides information to 1) estimate the optical axis in 3D world; 2) compute the geometry of the multi-camera system; 3) estimate the Point of Regard in 3D world. The resultant model is being used effectively to study visual attention by means of gaze estimation experiments, involving people performing natural tasks in wide-field, unstructured scenarios.

Algorithms for selective enumeration of prime implicants

Abstract We present a new approach for selective enumeration of prime implicants of CNF formulae. The method uses a 0–1 programming schema, having feasible solutions corresponding to prime implicants. Prime implicants are generated one at a time , so that as many of them can be computed as needed by the specific application considered. Selective generation is also supported, whereby preferences on the structure of generated prime implicants can be specified. We present two algorithms for selective enumeration of prime implicants and discuss their properties. The former amounts to solving the basic 0–1 programming schema first, to obtain an implicant ψ ′ (not necessarily a prime one), and then generating a prime implicant implied by ψ ′. The latter is based on adding a suitable minimization function to the basic 0–1 programming schema so that finding optimal solutions corresponds one-to-one to generating prime implicants of the original theory. We show that the latter algorithm has wider applicability but is less efficient than the former one. Finally we present experimental results, which confirm the effectiveness of our approach in computing prime implicants of CNF formulae.

Propositional Abduction in Modal Logic

In this work, the problem of performing abduction in modal logics is addressed, along the lines of 3], where a proof theoretical abduction method for full rst order classical logic is deened, based on tableaux and Gentzen-type systems. This work applies the same methodology to face modal abduction. The non-classical context enforces the value of analytical proof systems as tools to face the meta-logical and proof-theoretical questions involved in abductive reasoning. The similarities and diierences between quantiiers and modal operators are investigated and proof theoretical abduction methods for the modal systems K, D, T and S4 are deened, that are sound and complete. The construction of the abductive explanations is in strict relation with the expansion rules for the modal logics, in a modular manner that makes local modiications possible. The method given in this paper is general, in the sense that it can be adapted to any propositional modal logic for which analytic tableaux are provided. Moreover, the way towards an extension to rst order modal logic is straightforward.

Bottom-Up Gaze Shifts and Fixations Learning by Imitation

The ability to follow the gaze of conspecifics is a critical component in the development of social behaviors, and many efforts have been directed to studying the earliest age at which it begins to develop in infants. Developmental and neurophysiological studies suggest that imitative learning takes place once gaze-following abilities are fully established and joint attention can support the shared behavior required by imitation. Accordingly, gaze-following acquisition should be precursory to most machine learning tasks, and imitation learning can be seen as the earliest modality for acquiring meaningful gaze shifts and for understanding the structural substrate of fixations. Indeed, if some early attentional process, based on a suitable combination of gaze shifts and fixations, could be learned by the robot, then several demonstration learning tasks would be dramatically simplified. In this paper, we describe a methodology for learning gaze shifts based on imitation of gaze following with a gaze machine, which we purposefully introduced to make the robot gaze imitation conspicuous. The machine allows the robot to share and imitate gaze shifts and fixations of a caregiver through a mutual vergence. This process is then suitably generalized by learning both the scene salient features toward which the gaze is directed and the way saccadic programming is attained. Salient features are modeled by a family of Gaussian mixtures. These together with learned transitions are generalized via hidden Markov models to account for humanlike gaze shifts allowing to discriminate salient locations

Motion Saliency Maps from Spatiotemporal Filtering

For artificial systems acting and perceiving in a dynamic world a core ability is to focus on aspects of the environment that can be crucial for the task at hand. Perception in autonomous systems needs to be filtered by a biologically inspired selective ability, therefore attention in dynamic settings is becoming a key research issue. In this paper we present a model for motion salience map computation based on spatiotemporal filtering. We extract a measure of coherent motion energy and select by the center-surround mechanism relevant zones that accumulate most energy and therefore contrast with surroundings in a given time slot. The method was tested on synthetic and real video sequences, supporting biological plausibility.

A Proof Theoretical Approach to Default Reasoning I: Tableaux for Default Logic

We present a general proof theoretical methodology for default systems. Given a default theory 〈W, D〉, the default rules D are simply understood as restrictions on the tableaux construction of the logic. Different default approaches have their own way of understanding these restrictions and executing them. For each default approach (such as Reiter, Brewka or Lukaszewicz), the allowable default extensions can be obtained from the default tableau construction. The advantage of our approach, besides being simple and neat, is in its generality: it allows for the development of a default theory for any logic with a tableau formulation, such as intuitionistic logic, linear logic or modal logic.

A uniform tableau method for intuitionistic modal logics I

We present tableau systems and sequent calculi for the intuitionistic analoguesIK, ID, IT, IKB, IKDB, IB, IK4, IKD4, IS4, IKB4, IK5, IKD5, IK45, IKD45 andIS5 of the normal classical modal logics. We provide soundness and completeness theorems with respect to the models of intuitionistic logic enriched by a modal accessibility relation, as proposed by G. Fischer Servi. We then show the disjunction property forIK, ID, IT, IKB, IKDB, IB, IK4, IKD4, IS4, IKB4, IK5, IK45 andIS5. We also investigate the relationship of these logics with some other intuitionistic modal logics proposed in the literature.