Constraining application behaviour by generating languages

Writing a platform for reactive applications which enforces operational constraints is difficult, and has been approached in various ways. In this experience report, we detail an approach using an embedded DSL which can be used to specify the structure and permissions of a program in a given application domain. Once the developer has specified which components an application will consist of, and which permissions each one needs, the specification itself evaluates to a new, tailored, language. The final implementation of the application is then written in this specialised environment where precisely the API calls associated with the permissions which have been granted, are made available. Our prototype platform targets the domain of mobile computing, and is implemented using Racket. It demonstrates resource access control (e.g., camera, address book, etc.) and tries to prevent leaking of private data. Racket is shown to be an extremely effective platform for designing new programming languages and their run-time libraries. We demonstrate that this approach allows reuse of an inter-component communication layer, is convenient for the application developer because it provides high-level building blocks to structure the application, and provides increased control to the platform owner, preventing certain classes of errors by the developer.Comment: 8 pages, 8th European Lisp Symposiu

Agaat's Law. Reflections on Law and Literature with Reference to Marlene Van Niekerk's novel Agaat

This essay explores the relation between law and literature from the literary Marxist position that Jean-Luc Nancy develops in his work La Communauté Désoeuvrée. It does so with specific reference to Marlene van Niekerk’s novel Agaat and to the Lacanian problematic of imaginary selves caught up in the confines of their speculative or mirroring images of others. It takes leave of approaches to law and literature studies such as Martha Nussbaum’s in terms of which literature can be invoked to edify or improve the law. It argues that law and literature can both benefit from a comparative exchange, provided this exchange takes seriously the fundamental and irreducible tension and hiatus between characteristically “legal” and characteristically “literary” discourses

A Multidimensional Analysis of Poverty in the Eastern Cape Province, South Africa

This paper sets out the reasoning behind the fuzzy set approach to poverty measurement as a means to address both vertical and horizontal vagueness of poverty. The linear approach of Cerioli and Zani and the totally fuzzy and relative approach of Cheli and Lemmi are discussed and applied to the Eastern Cape Province, South Africa, using data from Census 96. The results indicate different experiences of poverty in the Eastern Cape. It is shown that the traditional money metric approach does not accurately identify the most deprived in society, indicating the importance of other non-metric dimensions in poverty measurement.multidimensional poverty, deprivation, well being, vagueness, measurement, fuzzy,

Pumping of the 4.8 GHz H2_{\text{2}}CO masers and its implications for the periodic masers in G37.55+0.20

Periodic or regular flaring of class II methanol masers in nine high mass star forming regions is now a well established phenomenon. Amongst the nine star forming regions, G37.55+0.20 is the only case at present where apart from the presence of a periodic class II methanol maser, correlated flaring of another masing species, formaldehyde in this case, has been detected. We perform numerical calculations to investigate under which conditions the 4.8 GHz transition of ortho-formaldehyde is inverted in order to address the question of the correlated flaring of the 6.7 GHz methanol and 4.8 GHz formaldehyde masers in G37.55+0.20. We developed a numerical code to study the population inversion of o-formaldehyde. Equilibrium solutions for the level populations are found by integrating the rate equations using Heun's method. It is found that collisional excitation with H$_2$ as well as radiative excitation by the free-free radio continuum radiation from a nearby ultra- or hyper-compact HII region can invert the 4.8 GHz transition. It is also found that radiative excitation by the dust infrared radiation field does not lead to an inversion of the 4.8 GHz transition. The 14.5 GHz and 28.9 GHz transitions are inverted only in the presence of the free-free continuum radiation field of a very compact HII region. Due to the different pumping mechanisms of the formaldehyde and methanol masers it is unlikely that the near simultaneous flaring of the methanol and formaldehyde masers in G37.55+0.20 is due to changes in the pumping of the masers.Comment: Accepted for publication in Astronomy and Astrophysic