Ordered Landmarks in Planning

Many known planning tasks have inherent constraints concerning the best order in which to achieve the goals. A number of research efforts have been made to detect such constraints and to use them for guiding search, in the hope of speeding up the planning process. We go beyond the previous approaches by considering ordering constraints not only over the (top-level) goals, but also over the sub-goals that will necessarily arise during planning. Landmarks are facts that must be true at some point in every valid solution plan. We extend Koehler and Hoffmann's definition of reasonable orders between top level goals to the more general case of landmarks. We show how landmarks can be found, how their reasonable orders can be approximated, and how this information can be used to decompose a given planning task into several smaller sub-tasks. Our methodology is completely domain- and planner-independent. The implementation demonstrates that the approach can yield significant runtime performance improvements when used as a control loop around state-of-the-art sub-optimal planning systems, as exemplified by FF and LPG

The identification and exploitation of almost symmetry in planning problems

Previous work in symmetry detection for planning has identified symmetries between domain objects and shown how the exploitation of this information can help reduce search at plan time. However these methods are unable to detect symmetries between objects that are almost symmetrical: where the objects must start (or end) in slightly different configurations but for much of the plan their behaviour is equivalent. In the paper we outline a method for identifying such symmetries and discuss how this symmetry information can be positively exploited to help direct search during planning we have implemented this method and integrated it with the FF-v2.3 planner and in the paper we present results of experiments with this approach that demonstrate its potential

Abstraction-based action ordering in planning

Many planning problems contain collections of symmetric objects, actions and structures which render them difficult to solve efficiently. It has been shown that the detection and exploitation of symmetric structure in planning problems can dramatically reduce the size of the search space and the time taken to find a solution. We present the idea of using an abstraction of the problem domain to reveal symmetric structure and guide the navigation of the search space. We show that this is effective even in domains in which there is little accessible symmetric structure available for pruning. Proactive exploitation represents a flexible and powerfulalternative to the symmetry-breaking strategies exploited in earlier work in planning and CSPs. The notion of almost symmetry is defined and results are presented showing that proactive exploitation of almost symmetry can improve the performance of a heuristic forward search planner

Versions of contemporary London staged in Westward Ho (1604), Eastward Ho (1605), and Northward Ho (1605)

My thesis researches, for the first time, the dialectical relationships between a cluster of plays performed at indoor playhouses in London immediately following the 1603-04 plague, in a capital radically impacted by population loss. These relationships are examined through an analysis of how the plays produce different versions of contemporary London and the degrees to which these are unlicensed or regulated. Building on the theoretical writings of de Certeau and the anthropologist Tim Ingold, I identify how versions of London are produced through the scope and significance of characters’ movements, through phenomenological and topographical excess, and through opportunities and agency afforded to women. In uncovering the playwrights’ responses to successive comedies I identify that these responses were increasingly a reaction to state surveillance. Dekker and Webster’s Westward Ho, performed at Paul’s, stages an innovative version of an open, unregulated London. A contextual analysis explains how the drama is grounded in a metatheatrical meshwork of theatregrams and tropes from plays performed from 1598-1603 set in modern London, yet produces a startlingly new version in which women are afforded unlicensed agency to create new situations and opportunities. I argue that Chapman, Jonson and Marston’s Eastward Ho at Blackfriars stands in antithetical opposition to Westward Ho. Eastward Ho, through satirising and parodying key elements of the first play, seeks to restore regulated civic and mercantile values. Dekker and Webster’s Northward Ho presents London life as a theatrical composition, where all is, potentially, a brand new play, circumventing authoritarian censorship and repression through a knowing metatheatrical artfulness. A final chapter considers how John Day’s The Isle of Gulls, 1606, follows the Ho plays, and engages with and satirises London’s new political scene by locating the drama in a foreign setting and, in a second distancing manoeuvre, turning back to pre-1598 generic conventions

The development of specialist support services for young people who have offended and who have also been victims of crime, abuse and/or violence: final report

This report presents the findings from research intended to inform the development of support services for young people who have offended and who have also been the victims of crime, abuse and/or violence. It was commissioned by the London Mayor's Office for Policing and Crime (MOPAC) which is funding the new services across twelve Youth Offending Teams in North and South London. It describes the findings from a survey of Youth Offending Team professionals and from an analysis of existing information on the needs of young people in these circumstances and outlines potential services for development

Ordered Landmarks in Planning

Many known planning tasks have inherent constraints concerning the best order in which to achieve the goals. A number of research efforts have been made to detect such constraints and to use them for guiding search, in the hope of speeding up the planning process. We go beyond the previous approaches by considering ordering constraints not only over the (top-level) goals, but also over the sub-goals that will necessarily arise during planning. Landmarks are facts that must be true at some point in every valid solution plan. We extend Koehler and Hoffmann's definition of reasonable orders between top level goals to the more general case of landmarks. We show how landmarks can be found, how their reasonable orders can be approximated, and how this information can be used to decompose a given planning task into several smaller sub-tasks. Our methodology is completely domain- and planner-independent. The implementation demonstrates that the approach can yield significant runtime performance improvements when used as a control loop around state-of-the-art sub-optimal planning systems, as exemplified by FF and LPG

Morphology and the gradient of a symmetric potential predicts gait transitions of dogs

Gaits and gait transitions play a central role in the movement of animals. Symmetry is thought to govern the structure of the nervous system, and constrain the limb motions of quadrupeds. We quantify the symmetry of dog gaits with respect to combinations of bilateral, fore-aft, and spatio-temporal symmetry groups. We tested the ability of symmetries to model motion capture data of dogs walking, trotting and transitioning between those gaits. Fully symmetric models performed comparably to asymmetric with only a 22% increase in the residual sum of squares and only one-quarter of the parameters. This required adding a spatio-temporal shift representing a lag between fore and hind limbs. Without this shift, the symmetric model residual sum of squares was 1700% larger. This shift is related to (linear regression, n = 5, p = 0.0328) dog morphology. That this symmetry is respected throughout the gaits and transitions indicates that it generalizes outside a single gait. We propose that relative phasing of limb motions can be described by an interaction potential with a symmetric structure. This approach can be extended to the study of interaction of neurodynamic and kinematic variables, providing a system-level model that couples neuronal central pattern generator networks and mechanical models