A Logic Your Typechecker Can Count On: Unordered Tree Types in Practice

Type systems featuring counting constraints are often stud- ied, but seldom implemented. We describe an efficient im- plementation of a type system for unordered, edge-labeled trees based on Presburger arithmetic constraints. We begin with a type system for unordered trees and give a compilation into counting automata. We then describe an optimized implementation that provides the fundamental operations of membership and emptiness testing. Although each operation has worst-case exponential complexity, we show how to achieve reasonable performance in practice using a combination of techniques, including syntactic translations, lazy automata unfolding, hash-consing, memoization, and incremental tree processing implemented using partial evaluation. These techniques avoid constructing and examining large structures in many cases and amortize the costs of expensive operations across many computations. To demonstrate the effectiveness of these optimizations, we present experimental data from executions on realistically sized examples drawn from the Harmony data synchronizer

Incremental View Maintenance For Collection Programming

In the context of incremental view maintenance (IVM), delta query derivation is an essential technique for speeding up the processing of large, dynamic datasets. The goal is to generate delta queries that, given a small change in the input, can update the materialized view more efficiently than via recomputation. In this work we propose the first solution for the efficient incrementalization of positive nested relational calculus (NRC+) on bags (with integer multiplicities). More precisely, we model the cost of NRC+ operators and classify queries as efficiently incrementalizable if their delta has a strictly lower cost than full re-evaluation. Then, we identify IncNRC+; a large fragment of NRC+ that is efficiently incrementalizable and we provide a semantics-preserving translation that takes any NRC+ query to a collection of IncNRC+ queries. Furthermore, we prove that incremental maintenance for NRC+ is within the complexity class NC0 and we showcase how recursive IVM, a technique that has provided significant speedups over traditional IVM in the case of flat queries [25], can also be applied to IncNRC+.Comment: 24 pages (12 pages plus appendix

Episodic Memory Measures Complement Structural and Functional MRI for Predicting Cognitive Decline in Apolipoprotein E ε4 Carriers

Apolipo-protein E (APOE) ?4 allele carriers demonstrate greater risk for cognitive decline and Alzheimer\u27s disease than non-carriers. However, factors associated with risk of decline among APOE ?4 carriers are not well-known. In this longitudinal study, we investigated whether discrete aspects of baseline episodic memory performance and structural (sMRI) and function (fMRI) magnetic resonance imaging were associated with cognitive decline in older APOE ?4 carriers and non-carriers. Seventy-eight healthy older adults underwent cognitive testing at baseline and after 18 months, baseline serum APOE genotyping, manually-traced hip-pocampal volume measurement from sMRI, and task-activated fMRI. Cognitive decline was defined as a one SD or greater reduction from baseline on at least one of three cognitive measures at follow-up (Rey Auditory Verbal Learning Test [AVLT] Delayed Recall and Trials 1-5 Sum, Mattis Dementia Rating Scale-2 Total Score). Declining APOE ?4 carriers (n=14) exhibited reduced hippocampal volume (

Observational learning of atypical biological kinematics in autism

Observing and voluntarily imitating the biological kinematics displayed by a model underpins the acquisition of new motor skills via sensorimotor processes linking perception with action. Differences in voluntary imitation in autism could be related to sensorimotor processing activity during action-observation of biological motion, as well as how sensorimotor integration processing occurs across imitation attempts. Using an observational practice protocol, which minimized the active contribution of the peripheral sensorimotor system, we examined the contribution of sensorimotor processing during action-observation. The data showed that autistic participants imitated both the temporal duration and atypical kinematic profile of the observed movement with a similar level of accuracy as neurotypical participants. These findings suggest the lower-level perception-action processes responsible for encoding biological kinematics during the action-observation phase of imitation are operational in autism. As there was no task-specific engagement of the peripheral sensorimotor system during observational practice, imitation difficulties in autism are most likely underpinned by sensorimotor integration issues related to the processing of efferent and (re)afferent sensorimotor information during trial-to-trial motor execution

Mechanized Metatheory for the Masses: The \u3cb\u3ePOPLMARK\u3c/b\u3e Challenge

How close are we to a world where every paper on programming languages is accompanied by an electronic appendix with machinechecked proofs? We propose an initial set of benchmarks for measuring progress in this area. Based on the metatheory of System F, a typed lambda-calculus with second-order polymorphism, subtyping, and records, these benchmarks embody many aspects of programming languages that are challenging to formalize: variable binding at both the term and type levels, syntactic forms with variable numbers of components (including binders), and proofs demanding complex induction principles. We hope that these benchmarks will help clarify the current state of the art, provide a basis for comparing competing technologies, and motivate further research

Using a coproduced educational workshop to change the focus of verbal instructions delivered by professional youth soccer coaches: a case study

Background The predominant instructional method utilised by soccer coaches are verbal instructions that occur whilst (during) players are executing soccer-skill. However, little is known on the specificity of the information contained within. These verbal instructions can guide the learner to either the performance characteristics of a movement (internal focus) or the intended movement effects (external), with the latter known to facilitate superior motor performance, retention, and transfer. Purpose The aims in the present study were to quantify the focus of concurrent verbal instructions utilised by professional youth soccer coaches during drill-based (i.e. isolated) practice activities, and to modulate how these instructions are delivered in coaching sessions following the engagement in a coproduced evidence-based educational workshop. Method Systematic observation was used pre and post the workshop to quantify the nature of verbal instructions delivered by 5 male coaches (31–47 years of age with 4–24 years of coaching experience) across 34 sessions with players from 8 to 13 years of age. For instructions provided during (concurrent) action-execution, we further quantified whether these instructions were focused on motor performance characteristics (internal) or the intended movement outcome effects (external) using criteria outlined in the revised Arizona State University Observation Instrument. To facilitate behaviour change, all coaches engaged in an educational workshop led by skill acquisition specialists (SAS). The workshop was designed so that educational material related to the principles of skill acquisition, and motor control and learning, were presented using a pedagogical delivery method containing verbal information, data presented in illustrations, and videos. In addition, the results that quantified coaching behaviour during the pre-workshop systematic observation period were presented to coaches as quantitative feedback. To guide the coaches to appraise the quantitative feedback in relation to the delivered educational material, the SAS built an educational environment that encouraged discussion opportunities for coaches to compare and appraise feedback with other coaches and process the feedback in relation to data and concepts regarding skill acquisition. Results and findings The pre-workshop systematic observation data indicated that coaches delivered significantly more (64%) verbal instructions whilst (concurrently) players were executing motor skills, compared to before (15%) or after (21%). Within concurrent feedback, coaches used instructions that had a more internal, compared to external focus of attention. Post-workshop data indicated the coaches significantly changed the utilisation of instructions using a greater proportion of external focus. The data confirms coaches deliver a greater proportion of concurrent verbal instructions during coaching sessions focused training drill-based activities, but engaging in an educational workshop coaches modulated the focus of these instructions from internal to external, indicating behaviour change and an opportunity to facilitate skill acquisition in soccer academy players