Cooperative Task Planning of Multi-Agent Systems Under Timed Temporal Specifications

In this paper the problem of cooperative task planning of multi-agent systems when timed constraints are imposed to the system is investigated. We consider timed constraints given by Metric Interval Temporal Logic (MITL). We propose a method for automatic control synthesis in a two-stage systematic procedure. With this method we guarantee that all the agents satisfy their own individual task specifications as well as that the team satisfies a team global task specification.Comment: Submitted to American Control Conference 201

Persistence and change in the spatio-temporal description of Sheffield Parish c.1750-1905

This paper brings a range of techniques from space syntax and fractal geometry to the question of the diachronic description of spatial structures that are usually considered in purely synchronic terms. Drawing on historical research into the growth of the English industrial city of Sheffield c.1770-1905 it asks how far the spatial configuration of the city’s rural hinterland (its ‘parish’) was implicated in the processes of social change and continuity that unfolded during this period. Time-series data on the development of Sheffield Parish is provided by the syntactical analysis of detailed historical maps, the routes taken by roadbased public transport systems and contemporary newspaper reports. The data is interpreted in the light of Hillier and Iida’s notion of angular, topological and metric “distance concepts” which are said to represent distinctive ‘modalities of scale’ in the emergence of an urban area embedded in the historical spatial configuration of its rural hinterland. In traditional urban geography the growth of cities is conventionally represented as the projection of an expanding built environment onto a blank surface. The discourse that accompanies this teleological notion of urbanization is typically one in which the countryside is ‘absorbed’ by the rapacious city. This language can be misleading, since urban areas whose growth can be regarded as ‘organic’ - in the sense of arising piecemeal over time - suggests the inadequacy of conceptualizing the built environment in a single (synchronic) dimension. The evidence from Sheffield Parish indicates how the differentiation of urban form is constituted both synchronically and diachronically in the description of spatial elements structured at different modalities of scale consistent with prevailing patterns of social practice, some of which relate to innovations in public transportation. The analysis of rural road networks represents a relatively new area of space syntax research. An historical study of this kind helps to ground future work by focusing on the emergent properties of space at the urban-rural periphery without also raising complex methodological questions relating to the application of space syntax methodology to large-scale contemporary urban regions. Rather, the emphasis is on drawing together the theoretical and analytical aspects of the Sheffield case study to assert that if the growing city is legitimately said to have ‘absorbed’ its rural hinterland then it is equally evident that this process of urban transformation can be also described in terms of the persistence of pre-urban road networks, historically embedded in local topography

Temporal similarity metrics for latent network reconstruction: The role of time-lag decay

When investigating the spreading of a piece of information or the diffusion of an innovation, we often lack information on the underlying propagation network. Reconstructing the hidden propagation paths based on the observed diffusion process is a challenging problem which has recently attracted attention from diverse research fields. To address this reconstruction problem, based on static similarity metrics commonly used in the link prediction literature, we introduce new node-node temporal similarity metrics. The new metrics take as input the time-series of multiple independent spreading processes, based on the hypothesis that two nodes are more likely to be connected if they were often infected at similar points in time. This hypothesis is implemented by introducing a time-lag function which penalizes distant infection times. We find that the choice of this time-lag strongly affects the metrics' reconstruction accuracy, depending on the network's clustering coefficient and we provide an extensive comparative analysis of static and temporal similarity metrics for network reconstruction. Our findings shed new light on the notion of similarity between pairs of nodes in complex networks

Probabilistically safe vehicle control in a hostile environment

In this paper we present an approach to control a vehicle in a hostile environment with static obstacles and moving adversaries. The vehicle is required to satisfy a mission objective expressed as a temporal logic specification over a set of properties satisfied at regions of a partitioned environment. We model the movements of adversaries in between regions of the environment as Poisson processes. Furthermore, we assume that the time it takes for the vehicle to traverse in between two facets of each region is exponentially distributed, and we obtain the rate of this exponential distribution from a simulator of the environment. We capture the motion of the vehicle and the vehicle updates of adversaries distributions as a Markov Decision Process. Using tools in Probabilistic Computational Tree Logic, we find a control strategy for the vehicle that maximizes the probability of accomplishing the mission objective. We demonstrate our approach with illustrative case studies

Time window temporal logic

This paper introduces time window temporal logic (TWTL), a rich expressive language for describing various time bounded specifications. In particular, the syntax and semantics of TWTL enable the compact representation of serial tasks, which are prevalent in various applications including robotics, sensor systems, and manufacturing systems. This paper also discusses the relaxation of TWTL formulae with respect to the deadlines of the tasks. Efficient automata-based frameworks are presented to solve synthesis, verification and learning problems. The key ingredient to the presented solution is an algorithm to translate a TWTL formula to an annotated finite state automaton that encodes all possible temporal relaxations of the given formula. Some case studies are presented to illustrate the expressivity of the logic and the proposed algorithms