We provide a syntax and a derivation system fora formal language of mathematics called Weak Type Theory (WTT). We give the metatheory of WTT and a number of illustrative examples.WTT is a refinement of de Bruijn''s Mathematical Vernacular (MV) and hence:– WTT is faithful to the mathematician''s language yet isformal and avoids ambiguities.

In an attempt to accommodate natural language phenomena involving nominalization and self-application, various researchers in formal semantics have proposed abandoning the hierarchical type system which Montague inherited from Russell, in favour of more flexible type regimes. We briefly review the main extant proposals, and then develop a new approach, based semantically on Aczel's notion of Frege structure, which implements a version ofsubsumption polymorphism. Nominalization is achieved by virtue of the fact that the types of predicative and propositional complements are contained (...) in the type of individuals. Russell's paradox is avoided by placing a type-constraint on lambda-abstraction, rather than by restricting comprehension. (shrink)

In this paper, a theory T H based on combining type freeness with logic is introduced and is then used to build a theory of properties which is applied to determiners and quantifiers.

In Russell''s Ramified Theory of Types RTT, two hierarchical concepts dominate:orders and types. The use of orders has as a consequencethat the logic part of RTT is predicative.The concept of order however, is almost deadsince Ramsey eliminated it from RTT. This is whywe find Church''s simple theory of types (which uses the type concept without the order one) at the bottom of the Barendregt Cube rather than RTT. Despite the disappearance of orders which have a strong correlation with predicativity, predicative (...) logic still plays an influential role in Computer Science.An important example is the proof checker Nuprl, which is basedon Martin-Löf''s Type Theory which uses type universes. Those type universes,and also degrees of expressions in AUTOMATH, are closely related toorders. In this paper, we show that orders have not disappeared from modern logic and computer science, rather, orders play a crucial role in understanding the hierarchy of modern systems. In order to achieve our goal, we concentrate on a subsystem of Nuprl.The novelty of our paper lies in: (1) a modest revival of Russell's orders, (2) the placing of the historical system RTT underlying the famous Principia Mathematica in a context with a modern system of computer mathematics (Nuprl) and modern type theories (Martin-Löf''s type theory and PTSs), and (3) the presentation of acomplex type system (Nuprl) as a simple and compact PTS. (shrink)

In this paper we consider a type system with a universal type $omega$ where any term (whether open or closed, $beta$-normalising or not) has type $omega$. We provide this type system with a realisability semantics where an atomic type is interpreted as the set of $lambda$-terms saturated by a certain relation. The variation of the saturation relation gives a number of interpretations to each type. We show the soundness and completeness of our semantics and that for different notions of saturation (...) (based on weak head reduction and normal $beta$-reduction) we obtain the same interpretation for types. Since the presence of $omega$ prevents typability and realisability from coinciding and creates extra difficulties in characterizing the interpretation of a type, we define a class ${mathbb U}^+$ of the so-called positive types (where $omega$ can only occur at specific positions). We show that if a term inhabits a positive type, then this term is $beta$-normalisable and reduces to a closed term. In other words, positive types can be used to represent abstract data types. The completeness theorem for ${mathbb U}^+$ becomes interesting indeed since it establishes a perfect equivalence between typable terms and terms that inhabit a type. In other words, typability and realisability coincide on ${mathbb U}^+$. We give a number of examples to explain the intuition behind the definition of ${mathbb U}^+$ and to show that this class cannot be extended while keeping its desired properties. (shrink)

The purpose of this paper is to provide a simple type-free set theory which can be used to give the various readings of collective/distributive sentences.

Typed λ-calculus uses two abstraction symbols which are usually treated in different ways: λx:*.x has as type the abstraction Πx:*.*, yet Πx:*.* has type □ rather than an abstraction; moreover, C is allowed and β-reduction evaluates it, but C is rarely allowed. Furthermore, there is a general consensus that λ and Π are different abstraction operators. While we agree with this general consensus, we find it nonetheless important to allow Π to act as an abstraction operator. Moreover, experience with AUTOMATH (...) and the recent revivals of Π-reduction as in [11, 14], illustrate the elegance of giving Π-redexes a status similar to λ-redexes. However, Π-reduction in the λ-cube faces serious problems as shown in [11, 14]: it is not safe as regards subject reduction, it does not satisfy type correctness, it loses the property that the type of an expression is well-formed and it fails to make any expression that contains a Π-redex well-formed. In this paper, we propose a solution to all those problems. The solution is to use a concept that is heavily present in most implementations of programming languages and theorem provers: abbreviations or let-expressions. We will show that the λ-cube extended with Π-conversion and abbreviations satisfies all the desirable properties of the cube and does not face any of the serious problems of Π-reduction. We believe that this extension of the λ-cube is very useful: it gives a full formal study of two concepts that are useful for theorem proving and programming languages. (shrink)

Types were invented by Russell to solve the logical paradoxes that resulted from Frege’s generalisaton of the notion of function. Since, the past 100 years saw new formalisations of the notions of functions and types that extend and put to better use Frege’s and Russell ’s inventions. Most such formalisations are extensions of Church’s simply typed λ-calculus. Currently, types and functions are the heart of logic and computation and not only are they so closely intertwined, but their evolution demands that (...) they be treated in the same manner. Both are usually constructed, abstracted over and instantiated and the operations for abstraction, construction, instantiation and substitution act alike on both. This paper aims to give a framework where the relationship between functions and types takes into account the similarity of their construction, abstraction, instantiation and substitution. For such a “types as functions” framework to work, special forms of function abstraction need to be included. (shrink)

In this article, we study the prehistory of type theory up to 1910 and its development between Russell and Whitehead's Principia Mathematica ([71], 1910-1912) and Church's simply typed λ-calculus of 1940. We first argue that the concept of types has always been present in mathematics, though nobody was incorporating them explicitly as such, before the end of the 19th century. Then we proceed by describing how the logical paradoxes entered the formal systems of Frege, Cantor and Peano concentrating on Frege's (...) Grundgesetze der Arithmetik for which Russell applied his famous paradox and this led him to introduce the first theory of types, the Ramified Type Theory (RTT). We present RTT formally using the modern notation for type theory and we discuss how Ramsey, Hilbert and Ackermann removed the orders from RTT leading to the simple theory of types STT. We present STT and Church's own simply typed λ-calculus (λ → C) and we finish by comparing RTT, STT and λ → C. (shrink)

The past decade has seen an explosion of work on calculi of explicit substitutions. Numerous works have illustrated the usefulness of these calculi for practical notions like the implementation of typed functional programming languages and higher order proof assistants. It has also been shown that eta-reduction is useful for adapting substitution calculi for practical problems like higher order unification. This paper concentrates on rewrite rules for eta-reduction in three different styles of explicit substitution calculi: λσ, λse and the suspension calculus. (...) Both λσ and λse when extended with eta-reduction rules, have proved useful for solving higher order unification. We enlarge the suspension calculus with an adequate eta-reduction rule which we show to preserve termination and confluence of the associated substitution calculus and to correspond to the eta rules of the other two calculi. We prove that λσ and λse as well as λσ and the suspension calculus are non-comparable while λse is more adequate than the suspension calculus in simulating one-step beta-reduction. After defining the eta-reduction rule in the suspension calculus, and after comparing these three calculi of explicit substitutions , we then concentrate on the implementation of the rewrite rules of eta-reduction in these calculi. We note that it is usual practice when implementing the eta rule for substitution calculi, to mix isolated applications of eta-reduction with the application of other rules of the corresponding substitution calculi. The main disadvantage of this practice is that the eta rewrite rules so obtained are unclean because they have an operational semantics different from that of the eta-reduction of the λ-calculus. For the three calculi in question enlarged with adequate eta rules we show how to implement these eta rules. For the λse we build a clean implementation of the eta rule and we prove that it is not possible to follow the same approach for the λσ and λsusp. (shrink)

The aim of the present study was to assess the impact of past traumatic war experiences on preadolescents in the Gaza Strip, which could be useful for psychological intervention with current and future child victims. Participants were 521 preadolescents from United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA) schools, aged 11 and 13 years old. Sections I to IV from Iraqi Version-Arabic of Harvard Trauma Questionnaire was used to assess trauma experiences and Post-Traumatic Stress (...) Disorder (PTSD). The results show that the preadolescents in the Gaza Strip witnessed the destruction of their homes and the murder of family members and friends. A quarter of the individuals assessed either suffered torture or witnessed others undergoing it, including sexual assaults. Almost half of them experienced a lack of food and clean water. The traumatic and torture experiences seriously affected preadolescents’ mental health as 26.29% met criteria for the diagnosis of PTSD. The data analysis revealed two PTSD modalities, with the severity of impact depending on whether social implications were involved. Further research is required to check whether these two modalities fit to PTSD and complex PTSD. Understanding the effects of past wars on preadolescents in Gaza and distinguishing between different PTSD types could enhance comprehension of the impacts of current attacks on child victims. It can also aid in determining the type of intervention needed to minimize the impact on the mental health of Palestinian youth, enhancing their resilience through psychological and social support. (shrink)

We present the system SUBSEXPL used for simulating and comparing explicit substitutions calculi. The system allows the manipulation of expressions of the λ-calculus and of three different styles of explicit substitutions: the λσ, the λse and the suspension calculus. A variation of the suspension calculus, which allows for combination of steps of β-contraction is included too. Implementations of the η-reduction are provided for each style. Other explicit substitutions calculi can be easily incorporated into the system due to its modular structure. (...) The uses of the system include: the visualization of the contractions of the λ-calculus in de Bruijn notation, and of guided one-step reductions as well as normalization via each of the associated substitution calculi. Many useful facilities are included: reductions can be easily recorded as text files, LATEX outputs can be generated and several examples for dealing with arithmetic operations and computational operators such as conditionals and repetitions in the λ-calculus are available. The system can be executed over Emacs using the x-symbol mode in such a way that λ-terms and terms of the explicit substitutions calculi are represented in its natural syntax avoiding the necessity of repeatedly generating LATEX outputs. The system has been of great help for systematically comparing explicit substitutions calculi, as well as for understanding properties of explicit substitutions such as the Preservation of Strong Normalization. In addition, it has been used for teaching basic properties of the λ-calculus such as: computational adequacy, the usefulness of de Bruijn's notation and of making explicit substitutions in real implementations. (shrink)

Background: Job satisfaction is largely associated with organizational aspects, including improved working environments, worker’s well-being and more effective performance. There are many definitions regarding job satisfaction in the existing scholarly literature: it can be expressed as a positive emotional state, a positive impact of job-related experiences on individuals, and employees’ perceptions regarding their jobs. Aims: No reliable scales in Arabic language to assess job satisfaction in the sports and physical education field exist.This study aimed to trans-culturally adapt and validate the (...) Pepe’s “Teacher Job Satisfaction Scale” 9 items (TJSS-9), creating the “Teacher of Physical Education Job Satisfaction Inventory” (TPEJSI) in Arabic language. This scale was administered to a Tunisian population of sports and physical education teachers and analyzed according to the Pepe’s theoretical model.. More in detail, this investigation systematically tested its factor structure, in terms of internal consistency/reliability, predictive validity, sensitivity and convergent validity. Methods: A total of 417 Tunisian teachers of sports and physical education participated voluntarily in this study. The sample comprised of 258 males and of 159 females. More in detail, 189 were teachers teaching in primary schools of physical education, 105 teaching in secondary schools, and 123 were university teachers. Both exploratory (EFA) and confirmatory (CFA) factor analyses were performed on random-split halves of the sample. Results: The three-dimensional alpha coefficients of the TPEJSI were all greater than 0.80: for satisfaction with colleagues, alpha was 0.865; for satisfaction with parents, alpha was 0.856 and for satisfaction with students alpha was 0.860. The CFA fit indices were satisfactory. Conclusions: Given the good EFA factor loadings, the CFA fit indices, the correlation matrix, the sensitivity analysis, the convergent validity and the excellent internal consistency, it can be concluded that the TPEJSI is a good psychometric tool that can be used to quantitatively assess the job satisfaction level among teachers of sports and physical education in the Arabic-speaking world. (shrink)

This paper described a formal theory of type judgments for propositional logic notations of PM; I felt the need of my own automated type checker to check their examples. The type checker I wrote did indeed serve to help me referee the paper, but also took a rather different approach to notation and typing for propositional functions of PM, which proved worth writing up independently in our own paper: Holmes, M. Randall, “Polymorphic type– checking for the ramified theory of types (...) of Principia Mathematica”, in Fairouz Kamareddine, ed., Thirty–five Years of Automating Mathematics, Kluwer, 2003, pp. 173-215. (shrink)

J. S. Silverberg, The Most Obscure and Inconvenient Tables ever Constructed.- D. J. Melville, Commercializing Arithmetic: The Case of Edward Hatton.- C. Baltus, Leading to Poncelet: A Story of Collinear Points.- R. Godard, Cauchy, Le Verrier et Jacobi sur le problème algébrique des valeurs propres et les inégalités séculaires des mouvements des planètes.- A. Ackerberg-Hastings, Mathematics in Astronomy at Harvard College Before 1839 as a Case Study for Teaching Historical Writing in Mathematics Courses.- J. J. Tattersall, S. L. McMurran, "Lectures (...) for Women" and the Founding of Newnham College, Cambridge.- D. Waszek, Are Euclid's Diagrams "Representations"? On an Argument by Ken Manders.- B. Buldt, Abstraction by Embedding and Constraint-Based Design.- W. Meyer, The Birth of Undergraduate Modern Algebra in the United States.- P. Liu, History as a Source of Mathematical Narrative in Developing Students' Interpretations of Mathematics.- F. Kamareddine, J. P. Seldin, Thoughts on Using the History of Mathematics to Teach the Foundations of Mathematical Analysis. (shrink)

This is a brief report on results reported at length in our paper [2], made for the purpose of a presentation at the workshop to be held in November 2011 in Cambridge on the Principia Mathematica of Russell and Whitehead ([?], hereinafter referred to briefly as PM ). That paper grew out of a reading of the paper [3] of Kamareddine, Nederpelt, and Laan. We refereed this paper and found it useful for checking their examples to write our own (...) independent computer type-checker for the type system of PM ([1]), which led us to think carefully about formalization of the language and the type system of PM A modern mathematical logician reading PM finds that it is not completely formalized in a modern sense. The type theory in particular is inarguably not formalized, as no notation for types is given at all! In PM itself, the only type annotations which appear are occasional numerical indices indicating order; the type notation we use here extends one introduced later by Ramsey. The authors of PM regard the absence of explicit indications of type as a virtue of their system: they call it “systematic ambiguity”; modern computer scientists refer to this as “polymorphism”. The language of PM is also not completely formalized, and it is typographically inconvenient for computer software to which ASCII input is to be given. The notation of PM for abstractions (propositional functions) does not use head binders; the order of the arguments of a complex expression is determined by the alphabetical order of the bound variables. For example ˆa < ˆb is the “less than” relation while ˆb < ˆa is the “greater than” relation (this is indicated by the alphabetical order of the variables). In PM , the fact that a variable is bound in a propositional function is indicated by circumflexing it. Variables bound by quantifiers are not circumflexed. A feature of the notation of [3], carried over into ours, is that no circumflexes are used: notations for propositions and the corresponding propositional functions are identical.. (shrink)