ASMs and Operational Algorithmic Completeness of Lambda Calculus

We show that lambda calculus is a computation model which can step by step simulate any sequential deterministic algorithm for any computable function over integers or words or any datatype. More formally, given an algorithm above a family of computable functions (taken as primitive tools, i.e., kind of oracle functions for the algorithm), for every constant K big enough, each computation step of the algorithm can be simulated by exactly K successive reductions in a natural extension of lambda calculus with constants for functions in the above considered family. The proof is based on a fixed point technique in lambda calculus and on Gurevich sequential Thesis which allows to identify sequential deterministic algorithms with Abstract State Machines. This extends to algorithms for partial computable functions in such a way that finite computations ending with exceptions are associated to finite reductions leading to terms with a particular very simple feature.Comment: 37 page

Hierarchical models for service-oriented systems

We present our approach to the denotation and representation of hierarchical graphs: a suitable algebra of hierarchical graphs and two domains of interpretations. Each domain of interpretation focuses on a particular perspective of the graph hierarchy: the top view (nested boxes) is based on a notion of embedded graphs while the side view (tree hierarchy) is based on gs-graphs. Our algebra can be understood as a high-level language for describing such graphical models, which are well suited for defining graphical representations of service-oriented systems where nesting (e.g. sessions, transactions, locations) and linking (e.g. shared channels, resources, names) are key aspects

A Focused Sequent Calculus Framework for Proof Search in Pure Type Systems

Basic proof-search tactics in logic and type theory can be seen as the root-first applications of rules in an appropriate sequent calculus, preferably without the redundancies generated by permutation of rules. This paper addresses the issues of defining such sequent calculi for Pure Type Systems (PTS, which were originally presented in natural deduction style) and then organizing their rules for effective proof-search. We introduce the idea of Pure Type Sequent Calculus with meta-variables (PTSCalpha), by enriching the syntax of a permutation-free sequent calculus for propositional logic due to Herbelin, which is strongly related to natural deduction and already well adapted to proof-search. The operational semantics is adapted from Herbelin's and is defined by a system of local rewrite rules as in cut-elimination, using explicit substitutions. We prove confluence for this system. Restricting our attention to PTSC, a type system for the ground terms of this system, we obtain the Subject Reduction property and show that each PTSC is logically equivalent to its corresponding PTS, and the former is strongly normalising iff the latter is. We show how to make the logical rules of PTSC into a syntax-directed system PS for proof-search, by incorporating the conversion rules as in syntax-directed presentations of the PTS rules for type-checking. Finally, we consider how to use the explicitly scoped meta-variables of PTSCalpha to represent partial proof-terms, and use them to analyse interactive proof construction. This sets up a framework PE in which we are able to study proof-search strategies, type inhabitant enumeration and (higher-order) unification

Человек, которого мучила бесконечность. О мудрости тургеневской

Het Zwanenwater anno 2011: heidevelden, meren, graslanden vol orchideeën, moerasplanten, wilgenstruweel en duingraslanden richting de zeereep. In hoeverre komt dit beeld overeen met dat van eind 19e eeuw, toen enkele natuurkenners na een urenlange reis dit gebied wisten te bereiken? Zijn de omstandigheden nu anders en kan aan de hand van de natuur inzicht worden verkregen in de veranderingsprocessen

SCC: A Service Centered Calculus

We seek for a small set of primitives that might serve as a basis for formalising and programming service oriented applications over global computers. As an outcome of this study we introduce here SCC, a process calculus that features explicit notions of service definition, service invocation and session handling. Our proposal has been influenced by Orc, a programming model for structured orchestration of services, but the SCC’s session handling mechanism allows for the definition of structured interaction protocols, more complex than the basic request-response provided by Orc. We present syntax and operational semantics of SCC and a number of simple but nontrivial programming examples that demonstrate flexibility of the chosen set of primitives. A few encodings are also provided to relate our proposal with existing ones

Strong Zonation of Benthic Communities Across a Tidal Freshwater Height Gradient

Trade-offs associated with environmental gradients generate patterns of diversity and govern community organisation in a landscape. In freshwaters, benthic community structure is driven by trade-offs along generally orthogonal gradients of habitat permanence and predation—where ephemeral systems are physiologically harsh because of drying stress, but inhabitants are less likely to be under the intense predation pressure of more permanent waterbodies. However, in tidal freshwaters, these two stressors are compounding, and the trade-offs associated with them are decoupled. 2. We investigated benthic community structure in a tidal freshwater habitat. These communities experience a suite of conditions atypical for a freshwater habitat: twice-daily drying; and high predation pressure by mobile fishes. We compared benthic communities at three tidal heights (low, mid, high) and contrasted these with nearby non-tidal freshwaters that varied in their hydrology (permanent, temporary). 3. We found that communities were more strongly differentiated in tidal freshwater habitats than between permanent and temporary inland freshwaters, which was surprising given the high interconnectedness and condensed longitudinal scale of tidal habitats. The differentiation of communities in tidal habitats was probably driven by the combined gradients of desiccation risk at low tide and intense predation by fish at high tide—a combination of pressures that are novel for the evolutionary history of the regional freshwater invertebrate fauna. 4. Our study provides evidence that environmental gradients can produce stronger patterns of community zonation than would be predicted for habitats that are spatially contiguous and have little or no dispersal limitation. These results give insight into how communities might respond if drivers of community structure are altered or reorganised from their regional or evolutionary norms

Human Hair Morphology: A Scanning Electron Microscopy Study on a Male Caucasoid and a Computerized Classification of Regional Differences

The present study was performed to provide a better understanding of the morphological variations of mammalian hair. Terminal hair samples were obtained from different regions of the body of the same Caucasian male. All hair samples were either cleaned or treated before being examined with scanning electron microscopy. As human scalp hair grew it appeared small like lanugo hair, but the increase in diameter appeared to have been relatively rapid. As hair increased in diameter the appearance of the scales changed. Neck hair was slightly smaller in diameter than scalp hair, and axillary hair was slightly smaller in diameter than neck hair. Nostril hair was larger than scalp or axillary hair. Eyelash hair was much smaller and much shorter than eyebrow hair. Neck hair, forearm hair, and shin hair were smaller than hair from most other regions of the body. Chest hair was similar in size to scalp hair, and pubic and sideburn hair were larger than scalp hair. A morphological feature called steak-boning was more characteristically present in whiskers of Caucasoids than Orientals or Blacks. Steak-boning occurred most frequently in hair of the mustache, followed by that of the chin, sideburn, cheek and under the chin. Cut surfaces of whiskers were different for electric as compared with straightedge razors. Hair morphology varied relative to the body region. Computer analysis of resin-embedded hair made it possible to classify arm, mustache, cheek, chin, head, shin, and pubic hair, and to quantify cross-sectioned differences

Оцінювання закону розподілу величини збитків унаслідок реалізації загрози “Відсутність або недостатність технічного обслуговування”

The problem of estimation of size distribution law of damages in the absence or insufficient sample size of the universe and the initial data suggested approach to finding the most expected value of losses due to information security threats

Estimating summary measures of health: a structured workbook approach

BACKGROUND: Summary measures of health that combine mortality and morbidity into a single indicator are being estimated in the Canadian context for approximately 200 diseases and conditions. To manage the large amount of data and calculations for this many diseases, we have developed a structured workbook system with easy to use tools. We expect this system will be attractive to researchers from other countries or regions of Canada who are interested in estimating the health-adjusted life years (HALYs) lost to premature mortality and year-equivalents lost to reduced functioning, as well as population attributable fractions (PAFs) associated with risk factors. This paper describes the workbook system using cancers as an example, and includes the entire system as a free, downloadable package. METHODS: The workbook system was developed in Excel and runs on a personal computer. It is a database system that stores data on population structure, mortality, incidence, distributions of cases entering a multitude of health states, durations of time spent in health states, preference scores that weight for severity, life table estimates of life expectancies, and risk factor prevalence and relative risks. The tools are Excel files with embedded macro programs. The main tool generates workbooks that estimate HALY, one per disease, by copying data from the database into a pre-defined template. Other tools summarize the HALY results across diseases for easy analysis. RESULTS: The downloadable zip file contains the database files initialized with Canadian data for cancers, the tools, templates and workbooks that estimate PAF and a user guide. The workbooks that estimate HALY are generated from the system at a rate of approximately one minute per disease. The resulting workbooks are self-contained and can be used directly to explore the details of a particular disease. Results can be discounted at different rates through simple parameter modification. CONCLUSION: The structured workbook approach offers researchers an efficient, easy to use, and easy to understand set of tools for estimating HALY and PAF summary measures for their country or region of interest