On the Execution of Ambients

Successfully harnessing multi-threaded programming has recently received renewed attention. The GHz war of the last years has been replaced with a parallelism war, each manufacturer seeking to produce CPUs supporting a greater number of threads in parallel execution. The Ambient calculus offers a simple yet powerful means to model communication, distributed computation and mobility. However, given its first class support for concurrency, we sought to investigate the utility of the Ambient calculus for practical programming purposes. Although too low-level to be considered as a general-purpose programming language itself, the Ambient calculus is nevertheless a suitable virtual machine for the execution of mobile and distributed higher-level languages. We present the Glint Virtual Machine: an interpreter for the Safe Boxed Ambient calculus. The GlintVM provides an effective platform for mobile, distributed and parallel computation and should ease some of the difficulties of writing compilers for languages that can exploit the new thread-parallel architectures

Safely Speaking in Tongues: Statically Checking Domain Specific Languages in Haskell

Haskell makes it very easy to build and use Domain Specific Languages (DSLs). However, it is frequently the case that a DSL has invariants that can not be easily enforced statically, resulting in runtime checks. This is a great pity given HaskellÆs rich and powerful type system and leads to all the usual problems of dynamic checking. We believe that Domain Specific Languages are becoming more popular: the internet itself is a good example of many DSLs (HTML, CSS, JavaScript, Flash, etc), and more seem to be being added every day; most graphics cards already accept programs written in the DSL OpenGL Shading Language (GLSL); and the predicted growth of heterogeneous CPUs (for example IBMÆs Cell CPU) will demand many different DSLs for the various programming models and instruction sets that become available. We present a technique that allows invariants of any given DSL to be lifted into the Haskell type system. This removes the need for runtime checks of the DSL and prevents programs that violate the invariants of the DSL from ever being compiled or executed. As a result we avoid the pitfalls of dynamic checking and return the user of the DSL to the safety and tranquillity of the strongly statically typed Haskell world

Session Types in Haskell: Updating Message Passing for the 21st Century

Session Types allow plans of conversation between two concurrent processes to be treated as types. Type checking then ensures that communication between processes is safe: i.e. it obeys the protocol specified by the session type. Thus Session Types offer a means to establish conformance to protocols in both distributed applications and multi-threaded programming. We incorporate Session Types into Haskell as a tool for concurrent programming. Our implementation, which is a standard Haskell library, presents a monadic API to the programmer. Using the library looks and feels very much like normal monadic computation and thus there is a shallow learning curve for the Haskell programmer. Our implementation lifts the invariants and properties of Session Types into Haskells rich type system. This allows our implementation to statically verify the use of the communication primitives provided without an additional type checker, preprocessor or modification to the compiler. Our implementation supports multiple concurrent communication channels, individual processes can interleave actions across any number of open channels, and channels themselves can be sent and received. New channels can be created between pre-existing processes as well as to newly created processes. Communication is asynchronous and fully polymorphic. To our knowledge, no other implementation of Session Types is available in any language which matches our library in terms of functionality and supported features. We describe the key aspects of our implementation and demonstrate, through a running example, its usage and flexibility

Errors for the Common Man: Hiding the unintelligable in Haskell

If a library designer takes full advantage of HaskellÆs rich type system and type-level programming capabilities, then the resulting library will frequently inflict huge and unhelpful error messages on the library user. These error messages are typically in terms of the library and do not refer to the call-site of the library by the library user, nor provide any guidance to the user as to how to fix the error. The increasing appetite for programmable type-level computation makes this a critical issue, as the advantages and capabilities of type-level computation are nullified if useful error messages cannot be returned to the user. We present a novel technique that neatly side-steps the default error messages and allows the library programmer to control the generation of error messages that are statically returned to the user. Thus with this technique, there is no longer any drawback to using the full power of HaskellÆs type system.Submitted versio

Softly safely spoken: Role playing for Session Types

Session types have made much progress at permitting programs be statically verified concordant with a specified protocol. However, it is difficult to build abstractions of, or encapsulate Session types, thus limiting their flexibility. Global session types add further constraints to communication, by permitting the order of exchanges amongst many participants to be specified. The cost is that the number of participants is statically fixed. We introduce Roles in which, similarly to global session types, the number of roles and the conversations involving roles are statically known, but participants can dynamically join and leave roles and the number of participants within a role is not statically known. Statically defined roles which conform to a specified conversation can be dynamically instantiated, participants can be members of multiple roles simultaneously and can participate in multiple conversations concurrently

The evaluation of (social-)psychological comfort in clothing, a possible approach

This paper presents the first results of a PhD research on psychological comfort of clothing. In order to understand and conceptualize the psychological aspects of clothing comfort, a variation of the Delphi Method was used to seek opinions from experts. This method was chosen because of its consensus-building features. The results were obtained from a qualitative text analysis, conducted over the experts’ responses to the first round of questions. The analytic process shed some light on the formation of the psychological comfort concept as well as the potential attributes to be evaluated when assessing this comfort dimension.This work is supported by FEDER funds through the Competitivity Factors Operational Programme - COMPETE and by national funds through FCT – Foundation for Science and Technology within the scope of the project POCI-01-0145-FEDER-007136. The first author would also like to gratefully acknowledge the support from the Araucaria Foundation of Paraná State and the Federal University of Technology, specially, the Fashion Design Department and the Office of Research and Graduate Studies.info:eu-repo/semantics/publishedVersio

How Well Do We (and Will We) Know Solar Neutrino Fluxes and Oscillation Parameters?

Assuming neutrino oscillations occur, the pp electron neutrino flux is uncertain by at least a factor of two, the ${\rm ^8B}$ flux by a factor of five, and the ${\rm ^7Be}$ flux by a factor of forty-five. Calculations of the expected results of future solar neutrino experiments (SuperKamiokande, SNO, BOREXINO, ICARUS, HELLAZ, and HERON) are used to illustrate the extent to which these experiments will restrict the range of the allowed neutrino mixing parameters. We present an improved formulation of the ``luminosity constraint'' and show that at 95\% confidence limit this constraint establishes the best available limits on the rate of creation of pp neutrinos in the solar interior and provides the best upper limit to the ${\rm ^7Be}$ neutrino flux.Comment: 37 pages, uuencoded Z-compressed postscript file (with figures); Submitted to Physical Review

Solar Neutrinos and the Principle of Equivalence

We study the proposed solution of the solar neutrino problem which requires a flavor nondiagonal coupling of neutrinos to gravity. We adopt a phenomenological point of view and investigate the consequences of the hypothesis that the neutrino weak interaction eigenstates are linear combinations of the gravitational eigenstates which have slightly different couplings to gravity, $f_1G$ and $f_2G$, $|f_1-f_2| << 1$, corresponding to a difference in red-shift between electron and muon neutrinos, $\Delta z/(1+z) \sim |f_1 - f_2|$. We perform a $\chi^2$ analysis of the latest available solar neutrino data and obtain the allowed regions in the space of the relevant parameters. The existing data rule out most of the parameter space which can be probed in solar neutrino experiments, allowing only $|f_1 - f_2| \sim 3 \times 10^{-14}$ for small values of the mixing angle ($2 \times 10^{-3} \le \sin^2(2\theta_G) \le 10^{-2}$) and $10^{-16} \stackrel{<}{\sim} |f_1 - f_2| \stackrel{<}{\sim}10^{-15}$ for large mixing ($0.6 \le \sin^2(2\theta_G) \le 0.9$). Measurements of the $^8{\rm B}$-neutrino energy spectrum in the SNO and Super-Kamiokande experiments will provide stronger constraints independent of all considerations related to solar models. We show that these measurements will be able to exclude part of the allowed region as well as to distinguish between conventional oscillations and oscillations due to the violation of the equivalence principle.Comment: 20 pages + 4 figures, IASSNS-AST 94/5

Constraints on neutrino oscillation parameters from the measurement of day-night solar neutrino fluxes at Super-Kamiokande

A search for day-night variations in the solar neutrino flux resulting from neutrino oscillations has been carried out using the 504 day sample of solar neutrino data obtained at Super-Kamiokande. The absence of a significant day-night variation has set an absolute flux independent exclusion region in the two neutrino oscillation parameter space.Comment: 11 pages, 3 figures, submitted to PRL, single-spacin

Neutrino masses: From fantasy to facts

Theory suggests the existence of neutrino masses, but little more. Facts are coming close to reveal our fantasy: solar and atmospheric neutrino data strongly indicate the need for neutrino conversions, while LSND provides an intriguing hint. The simplest ways to reconcile these data in terms of neutrino oscillations invoke a light sterile neutrino in addition to the three active ones. Out of the four neutrinos, two are maximally-mixed and lie at the LSND scale, while the others are at the solar mass scale. These schemes can be distinguished at neutral-current-sensitive solar & atmospheric neutrino experiments. I discuss the simplest theoretical scenarios, where the lightness of the sterile neutrino, the nearly maximal atmospheric neutrino mixing, and the generation of $\Delta {m^2}_\odot$ & $\Delta {m^2}_{atm}$ all follow naturally from the assumed lepton-number symmetry and its breaking. Although the most likely interpretation of the present data is in terms of neutrino-mass-induced oscillations, one still has room for alternative explanations, such as flavour changing neutrino interactions, with no need for neutrino mass or mixing. Such flavour violating transitions arise in theories with strictly massless neutrinos, and may lead to other sizeable flavour non-conservation effects, such as $\mu \to e + \gamma$, $\mu-e$ conversion in nuclei, unaccompanied by neutrino-less double beta decay.Comment: 33 pages, latex, 16 figures. Invited Talk at Ioannina Conference, Symmetries in Intermediate High Energy Physics and its Applications, Oct. 1998, to be published by Springer Tracts in Modern Physics. Festschrift in Honour of John Vergados' 60th Birthda