Nominal techniques

This is the author accepted manuscript. The final version is available from the Association for Computing Machinery via http://dx.doi.org/10.1145/2893582.2893594 Programming languages abound with features making use of names in various ways. There is a mathematical foundation for the semantics of such features which uses groups of permutations of names and the notion of the support of an object with respect to the action of such a group. The relevance of this kind of mathematics for the semantics of names is perhaps not immediately obvious. That it is relevant and useful has emerged over the last 15 years or so in a body of work that has acquired its own name: nominal techniques. At the same time, the application of these techniques has broadened from semantics to computation theory in general. This article introduces the subject and is based upon a tutorial at LICS-ICALP 2015 [Pitts 2015a]. </jats:p

Fresh-Register Automata

What is a basic automata-theoretic model of computation with names and fresh-name generation? We introduce Fresh-Register Automata (FRA), a new class of automata which operate on an infinite alphabet of names and use a finite number of registers to store fresh names, and to compare incoming names with previously stored ones. These finite machines extend Kaminski and Francez’s Finite-Memory Automata by being able to recognise globally fresh inputs, that is, names fresh in the whole current run. We exam-ine the expressivity of FRA’s both from the aspect of accepted languages and of bisimulation equivalence. We establish primary properties and connections between automata of this kind, and an-swer key decidability questions. As a demonstrating example, we express the theory of the pi-calculus in FRA’s and characterise bisimulation equivalence by an appropriate, and decidable in the finitary case, notion in these automata

Migration Planning Among Female Prospective Labour Migrants from Nepal: A Comparison of First-Time and Repeat-Migrants

As international female labour migration has increased, so too have efforts to prevent the exploitation of labour migrants. However, evidence to underpin prevention efforts remains limited, with little known about labour migrants’ migration planning processes. Using data from a survey of female prospective labour migrants from Nepal, this article compares socio-demographics and migration-planning processes between first-time and repeat-migrants. We identified several factors which might increase repeat-migrants’ vulnerability to exploitation during the migration process, or obstruct their engagement in pre-migration interventions: more rapid migration planning than first-time migrants; lower involvement in community groups; and a perception that they already have the knowledge they need. Only one-third of repeat-migrants planned to go to the same destination and 42 per cent to work in the same sector as previously. With repeat-migration a common livelihoods strategy, it is crucial that interventions are guided by evidence on the needs of both first-time- and repeat-migrants

Denotational semantics with nominal scott domains

When defining computations over syntax as data, one often runs into tedious issues concerning α -equivalence and semantically correct manipulations of binding constructs. Here we study a semantic framework in which these issues can be dealt with automatically by the programming language. We take the user-friendly “nominal” approach in which bound objects are named. In particular, we develop a version of Scott domains within nominal sets and define two programming languages whose denotational semantics are based on those domains. The first language, λν -PCF, is an extension of Plotkin’s PCF with names that can be swapped, tested for equality and locally scoped; although simple, it already exposes most of the semantic subtleties of our approach. The second language, PNA, extends the first with name abstraction and concretion so that it can be used for metaprogramming over syntax with binders. For both languages, we prove a full abstraction result for nominal Scott domains analogous to Plotkin’s classic result about PCF and conventional Scott domains: two program phrases have the same observable operational behaviour in all contexts if and only if they denote equal elements of the nominal Scott domain model. This is the first full abstraction result we know of for languages combining higher-order functions with some form of locally scoped names which uses a domain theory based on ordinary extensional functions, rather than using the more intensional approach of game semantics. To obtain full abstraction, we need to add two functionals, one for existential quantification over names and one for “definite description” over names. Only adding one of them is not enough, as we give counter-examples to full abstraction in both cases.This work is supported by a Gates Cambridge Scholarship and the ERC Advanced Grant Events, Causality and Symmetry (ECSYM)This version is the author accepted manuscript. The final version is available from ACM at http://dl.acm.org/citation.cfm?id=2629529

Resource-Bound Quantification for Graph Transformation

Graph transformation has been used to model concurrent systems in software engineering, as well as in biochemistry and life sciences. The application of a transformation rule can be characterised algebraically as construction of a double-pushout (DPO) diagram in the category of graphs. We show how intuitionistic linear logic can be extended with resource-bound quantification, allowing for an implicit handling of the DPO conditions, and how resource logic can be used to reason about graph transformation systems

Correctional Officers\u27 Perceptions of Working with Inmates with Mental Illnesses and the Effectiveness of Mental Health Training

Many correctional officers have voiced not receiving adequate training in mental health and how to best work with inmates who may be experiencing mental health symptoms. Crisis Intervention Team (CIT) training has improved officers’ responses to working with individuals during a mental health crisis The purpose of this project was to examine correctional officers’ perceptions of working with inmates with mental illnesses and how prepared they feel working with inmates who are in crisis. Seventy correctional officers were surveyed in two county jails in Minnesota. The sample of participants included officers who have been certified in CIT. Results were analyzed using descriptive and inferential statistics. While findings indicated there were no differences in perceptions of inmates with mental illnesses between correctional officers certified in CIT and correctional officers who were not, correctional officers who were certified in CIT self-reported they felt more prepared to work with inmates experiencing mental health symptoms and inmates who were in crisis. A third finding demonstrated correctional officers who indicated they were prepared to work with these inmates also had more positive perceptions of them. The participants surveyed were unrepresentative across gender and race. Conducting further research will help gain a better understanding on the views correctional officers have towards mental illnesses and responding to inmates who have mental illnesses, or who are in crisis