Generating Efficient, Terminating Logic Programs

The objective of control generation in logic programming is to automatically derive a computation rule for a program that is efficient and yet does not compromise program correctness. Progress in solving this important problem has been slow and, to date, only partial solutions have been proposed where the generated programs are either incorrect or inefficient. We show how the control generation problem can be tackled with a simple automatic transformation that relies on information about the depths of derivations. To prove correctness of our transform we introduce the notion of a semi delay recurrent program which generalises previous ideas in the termination literature for reasoning about logic programs with dynamic selection rules

Typed Norms for Typed Logic Programs

As typed logic programming becomes more mainstream, system building tools like partial deduction systems will need to be mapped from untyped languages to typed ones. It is important, however, when mapping techniques across that the new techniques should exploit the type system as much as possible. in this paper, we show how norms which play a crucial role in termination analysis, can be generated from the prescribed types of a logic program. Interestingly, the types highlight restrictions of earlier norms and suggest how these norms can be extended to obtain some very general and powerful notions of norm which can be used to measure any term in an almost arbitrary way. We see our work on norm derivation as a contribution to the termination analysis of typed logic programs which, in particular, forms an essential part of offline partial deduction systems

The end of the map?

Martin Smith and Andy Howard* explain why moving away from the printed map to a digital 3D National Geological Model is a ‘coming of age’ for William Smith’s great visio

Control Generation by Program Transformation

The objective of control generation in logic programming is to derive a computation rule for a program that is efficient and yet does not compromise program correctness. Progress in solving this fundamental problem in logic programming has been slow and, to date, only partial solutions have been proposed. Previously proposed schemes are either inefficient, incomplete (incorrect) or difficult to apply for programs consisting of many components (the scheme is not modular). This paper shows how the control generation problem can be tackled by program transformation. The transformation relies on information about the depths of derivations to derive delay declarations which orchestrate the control. To prove correctness of the transformation, the notion of semi-delay recurrency is introduced, which generalises previous ideas in the termination literature for reasoning about logic programs with delay declarations. In contrast to previous work, semi-delay recurrency does not require an atom to be completely resolved before another is selected for reduction. This enhancement permits the transformation to introduce control which is flexible and relatively efficient

Lessons from civil society: how a ‘Theory of Change’ can help tell a bigger impact story.

As academics think about impact, they can draw on some of the lessons and strategic approaches used by civil society and campaigning groups. Andy Martin, Director of strategy consulting firm Firetail, says academics should ask themselves three questions when thinking about the impact of their research to help form a broader understanding of how their work operates beyond reductive measurables

Fermionic Operator Mixing in Holographic p-wave Superfluids

We use gauge-gravity duality to compute spectral functions of fermionic operators in a strongly-coupled defect field theory in p-wave superfluid states. The field theory is (3+1)-dimensional N=4 supersymmetric SU(Nc) Yang-Mills theory, in the 't Hooft limit and with large coupling, coupled to two massless flavors of (2+1)-dimensional N=4 supersymmetric matter. We show that a sufficiently large chemical potential for a U(1) subgroup of the global SU(2) isospin symmetry triggers a phase transition to a p-wave superfluid state, and in that state we compute spectral functions for the fermionic superpartners of mesons valued in the adjoint of SU(2) isospin. In the spectral functions we see the breaking of rotational symmetry and the emergence of a Fermi surface comprised of isolated points as we cool the system through the superfluid phase transition. The dual gravitational description is two coincident probe D5-branes in AdS5 x S5 with non-trivial worldvolume SU(2) gauge fields. We extract spectral functions from solutions of the linearized equations of motion for the D5-branes' worldvolume fermions, which couple to one another through the worldvolume gauge field. We develop an efficient method to compute retarded Green's functions from a system of coupled bulk fermions. We also perform the holographic renormalization of free bulk fermions in any asymptotically Euclidean AdS space.Comment: 68 pages, 25 eps files in 9 figures; v2 minor corrections, added two references, version published in JHE

Combining semantic and syntactic generalization in example-based machine translation

In this paper, we report our experiments in combining two EBMT systems that rely on generalized templates, Marclator and CMU-EBMT, on an English–German translation task. Our goal was to see whether a statistically significant improvement could be achieved over the individual performances of these two systems. We observed that this was not the case. However, our system consistently outperformed a lexical EBMT baseline system

Reaping the rewards of learning within agricultural knowledge systems: An account of a PhD learning system

Despite the existence and application of mandatory agri-environmental policy for many decades, significant environmental sustainability problems remain attributable to the agricultural sector. Participatory types of extension practices are believed to have a potential to enable extension organisations to enhance the supports provided to farmers to help meet the requirements and objectives of these policies. To test this proposition, the PhD researcher used a learning systems approach for exploring the interplay between farmer subjectivities, the European Union’s policy of cross compliance and the extension practices of Teagasc, the Irish Agriculture and Food Development Authority. Three learning sub-systems were employed in the investigation. The first used the principles of Participatory Action Research for revealing stakeholders’ perceptions of Teagasc’s cross compliance extension service. This process resulted in the attainment of rich insights about extension practices, however it also revealed that a significant number of farmers were experiencing socio-cultural difficulties with the application and enforcement of cross compliance. To better understand the implications of these subjectivities, a second sub-system was created to learn about farmers’ experiences of the policy. This process surfaced diverse insights about farmers’ personal experiences of cross compliance. A final sub-system employed systems thinking and practice for appraising the utility of the learning arising from the previous sub-systems for improving interactions between farmers, extension organisations and cross compliance. The combined findings of the thesis indicate that there is considerable potential for extension organisations to use participatory practices for developing rich understandings of farmers’ preferences for mandatory agri-environmental policy and its related extension practices. However, a limitation in realising participant preferences is that extension organisations appear to have little influence over the application and enforcement of mandatory agri-environmental policy. Overcoming this participatory barrier will require sustained collective learning targeted at understanding how stakeholders can work together to develop agri-environmental policies that are socially, financially and environmentally sustainable. This paper explores how this ‘sustained collective learning’ may be realised taking a specific account of the learnings developed within and following the completion of the PhD Learning System. The insights elucidated will be of interest to scholars and extension practitioners involved in similar learning endeavours

New method to study the repellent, irritant and toxic effects on Anopheles gambiae. Application on 20 essential oils

Laboratory and field studies showed that repellent and irritant actions of common public health insecticides reduce the man-vector contact and so interrupt the disease transmission particularly when use with long lasting treated bednets. However resistance in mosquitoe populations bring up the issue of finding alternative to these insecticides. The objective of this study was to evaluate the repellent, irritant and toxic effects of 20 essential oils on Anopheles gambiae adults in laboratory. A high-troughput screening system was previously described to characterize repellent, irritant and toxicant chemical actions on Aedes spp. This system was adapted to test essential oils on An. gambiae. Twenty essentials oils were tested on An. gambiae at three concentrations (0.01%, 0.1% and 1%) with 3 replications of 20 adult mosquitoes. Results showed essential oils could have irritant, repellent, or toxic effects on An. gambiae. But data also indicated that behavioral responses to the three effects appeared independent so we could expect that the repellent mechanism may be different than the irritant and than the toxic ones. However the behavioral response of An. gambiae was dose-dependent. (Texte intégral