Typed open programming : a higher-order, typed approach to dynamic modularity and distribution

In this dissertation we develop an approach for reconciling open programming the development of programs that support dynamic exchange of higher-order values with other processes with strong static typing in programming languages. We present the design of a concrete programming language, Alice ML, that consists of a conventional functional language extended with a set of orthogonal features like higher-order modules, dynamic type checking, higher-order serialisation, and concurrency. On top of these a flexible system of dynamic components and a simple but expressive notion of distribution is realised. The central concept in this design is the package, a first-class value embedding a module along with its interface type, which is dynamically checked whenever the module is extracted. Furthermore, we develop a formal model for abstract types that is not invalidated by the presence of primitives for dynamic type inspection, as is the case for the standard model based on existential quantification. For that purpose, we present an idealised language in form of an extended -calculus, which can express dynamic generation of types. This calculus is the first to combine and explore the interference of sealing and type inspection with higher-order singleton kinds, a feature for expressing sharing constraints on abstract types. A novel notion of abstracton kinds classifies abstract types. Higher-order type and kind coercions allow for modular translucent encapsulation of values at arbitrary type.In dieser Dissertation entwickeln wir einen programmiersprachlichen Ansatz zur Verbindung offener Programmierung der Entwicklung von Programmen, die das dynamische Laden und Austauschen höherstufiger Werte mit anderen Prozessen erlauben mit starker statischer Typisierung. Wir stellen das Design einer konkreten Programmiersprache namens Alice ML vor. Sie besteht aus einer konventionellen funktionalen Sprache, die um einen Satz orthogonaler Konzepte wie höherstufige Modularisierung, dynamische Typüberprüfung, höherstufige Serialisierung und Nebenläufigkeit erweitert wurde. Darauf aufbauend ist ein flexibles System dynamischer Komponenten sowie ein einfacher aber expressiver Ansatz fur Verteilung verwirklicht. Zentral ist dabei das Konzept eines Pakets (package), welches ein Modul in Kombination mit seinem Schnittstellentyp in einen Wert einbettet, und bei der Extraktion des Moduls eine dynamische Typüberprüfung vornimmt. Weiterhin entwickeln wir einen theoretischen Ansatz zur Modellierung von abstrakten Typen, welcher im Gegensatz zum herkömmlichen formalen Modell existentieller Quantifizierung auch in Gegenwart dynamischer Typinspektion gültig ist. Zu diesem Zweck definieren wir eine idealisierte Sprache in Form eines erweiterten λ-Kalküls, der dynamische Typgenerierung ausdrucken kann. Der Kalkül kombiniert diese erstmals mit höherstufigen Singleton Kinds, einem Sprachkonstrukt, welches Gleichheit von Typen ausdrücken kann. Zur Klassifizierung abstrakter Typen werden Abstraktions-Kinds als verwandtes Konzept entwickelt. Höherstufige Konversionen auf Term- und Typebene erlauben zudem die nachträgliche modulare Enkapsulierung von Werten beliebigen Typs

Pure subtype systems: a type theory for extensible software

This thesis presents a novel approach to type theory called “pure subtype systems”, and a core calculus called DEEP which is based on that approach. DEEP is capable of modeling a number of interesting language techniques that have been proposed in the literature, including mixin modules, virtual classes, feature-oriented programming, and partial evaluation. The design of DEEP was motivated by two well-known problems: “the expression problem”, and “the tag elimination problem.” The expression problem is concerned with the design of an interpreter that is extensible, and requires an advanced module system. The tag elimination problem is concerned with the design of an interpreter that is efficient, and requires an advanced partial evaluator. We present a solution in DEEP that solves both problems simultaneously, which has never been done before. These two problems serve as an “acid test” for advanced type theories, because they make heavy demands on the static type system. Our solution in DEEP makes use of the following capabilities. (1) Virtual types are type definitions within a module that can be extended by clients of the module. (2) Type definitions may be mutually recursive. (3) Higher-order subtyping and bounded quantification are used to represent partial information about types. (4) Dependent types and singleton types provide increased type precision. The combination of recursive types, virtual types, dependent types, higher-order subtyping, and bounded quantification is highly non-trivial. We introduce “pure subtype systems” as a way of managing this complexity. Pure subtype systems eliminate the distinction between types and objects; every term can behave as either a type or an object depending on context. A subtype relation is defined over all terms, and subtyping, rather than typing, forms the basis of the theory. We show that higher-order subtyping is strong enough to completely subsume the traditional type relation, and we provide practical algorithms for type checking and for finding minimal types. The cost of using pure subtype systems lies in the complexity of the meta-theory. Unfortunately, we are unable to establish some basic meta-theoretic properties, such as type safety and transitivity elimination, although we have made some progress towards these goals. We formulate the subtype relation as an abstract reduction system, and we show that the type theory is sound if the reduction system is confluent. We can prove that reductions are locally confluent, but a proof of global confluence remains elusive. In summary, pure subtype systems represent a new and interesting approach to type theory. This thesis describes the basic properties of pure subtype systems, and provides concrete examples of how they can be applied. The Deep calculus demonstrates that our approach has a number of real-world practical applications in areas that have proved to be quite difficult for traditional type theories to handle. However, the ultimate soundness of the technique remains an open question

Formal foundations for hybrid effect analysis

Type-and-effect systems are a powerful tool for program construction and verification. Type-and-effect systems are useful because it can help reduce bugs in computer programs, enable compiler optimizations and also provide sort of program documentation. As software systems increasingly embrace dynamic features and complex modes of compilation, static effect systems have to reconcile over competing goals such as precision, soundness, modularity, and programmer productivity. In this thesis, we propose the idea of combining static and dynamic analysis for effect systems to improve precision and flexibility. We describe intensional effect polymorphism, a new foundation for effect systems that integrates static and dynamic effect checking. Our system allows the effect of polymorphic code to be intensionally inspected. It supports a highly precise notion of effect polymorphism through a lightweight notion of dynamic typing. When coupled with parametric polymorphism, the powerful system utilizes runtime information to enable precise effect reasoning, while at the same time retains strong type safety guarantees. The technical innovations of our design include a relational notion of effect checking, the use of bounded existential types to capture the subtle interactions between static typing and dynamic typing, and a differential alignment strategy to achieve efficiency in dynamic typing. We introduce the idea of first-class effects, where the computational effect of an expression can be programmatically reflected, passed around as values, and analyzed at run time. A broad range of designs “hard-coded in existing effect-guided analyses can be supported through intuitive programming abstractions. The core technical development is a type system with a couple of features. Our type system provides static guarantees to application-specific effect management properties through refinement types, promoting “correct-by-design effect-guided programming. Also, our type system computes not only the over-approximation of effects, but also their under-approximation. The duality unifies the common theme of permission vs. obligation in effect reasoning. Finally, we show the potential benefit of intensional effects by applying it to an event-driven system to obtain safe concurrency. The technical innovations of our system include a novel effect system to soundly approximate the dynamism introduced by runtime handlers registration, a static analysis to precompute the effects and a dynamic analysis that uses the precomputed effects to improve concurrency. Our design simplifies modular concurrency reasoning and avoids concurrency hazards

Dynamic Translucency with Abstraction Kinds and Higher-order Coercions

When a module language is combined with forms of non-parametric type analysis, abstract types require an opaque dynamic representation in order to maintain abstraction safety. As an idealisation of such a module language, we present a foundational calculus that combines higher-order type generation, modelling type abstraction, with singleton kinds, modelling translucency. In this calculus, type analysis can dynamically exploit translucency, without breaking abstraction. Abstract types are classified by a novel notion of abstraction kinds. These are analogous to singletons, but instead of inducing equivalence they induce an isomorphism that is witnessed by explicit type coercions on the term level. To encompass higher-order forms of translucent abstraction, we give an account for higher-order coercions in a rich type system with higher-order polymorphism and dependent kinds. The latter necessitate the introduction of an analogous notion of kind coercions on the type level. Finally, we give an abstraction-safe encoding of ML-style module sealing in terms of higher-kinded type generation and higher-order coercion

Art in the Anthropocene: Encounters Among Aesthetics, Politics, Environments and Epistemologies

Taking as its premise that the proposed geologic epoch of the Anthropocene is necessarily an aesthetic event, this book explores the relationship between contemporary art and knowledge production in an era of ecological crisis, with contributions from artists, curators, theorists and activists. Contributors include Amy Balkin, Ursula Biemann, Amanda Boetzkes, Lindsay Bremner, Joshua Clover & Juliana Spahr, Heather Davis, Sara Dean, Elizabeth Ellsworth & Jamie Kruse (smudge studio), Irmgard Emmelhainz, Anselm Franke, Peter Galison, Fabien Giraud & Ida Soulard, Laurent Gutierrez & Valérie Portefaix (MAP Office), Terike Haapoja & Laura Gustafsson, Laura Hall, Ilana Halperin, Donna Haraway & Martha Kenney, Ho Tzu Nyen, Bruno Latour, Jeffrey Malecki, Mary Mattingly, Mixrice (Cho Jieun & Yang Chulmo), Natasha Myers, Jean-Luc Nancy & John Paul Ricco, Vincent Normand, Richard Pell & Emily Kutil, Tomás Saraceno, Sasha Engelmann & Bronislaw Szerszynski, Ada Smailbegovic, Karolina Sobecka, Zoe Todd, Richard Streitmatter-Tran & Vi Le, Anna-Sophie Springer, Sylvère Lotringer, Peter Sloterdijk, Etienne Turpin, Pinar Yoldas, and Una Chaudhuri, Fritz Ertl, Oliver Kellhammer & Marina Zurkow

Art in the Anthropocene: Encounters among aesthetics, politics, environments and epistemologies

Taking as its premise that the proposed geologic epoch of the Anthropocene is necessarily an aesthetic event, this book explores the relationship between contemporary art and knowledge production in an era of ecological crisis, with contributions from artists, curators, theorists and activists. Contributors include Amy Balkin, Ursula Biemann, Amanda Boetzkes, Lindsay Bremner, Joshua Clover & Juliana Spahr, Heather Davis, Sara Dean, Elizabeth Ellsworth & Jamie Kruse (smudge studio), Irmgard Emmelhainz, Anselm Franke, Peter Galison, Fabien Giraud & Ida Soulard, Laurent Gutierrez & Valérie Portefaix (MAP Office), Terike Haapoja & Laura Gustafsson, Laura Hall, Ilana Halperin, Donna Haraway & Martha Kenney, Ho Tzu Nyen, Bruno Latour, Jeffrey Malecki, Mary Mattingly, Mixrice (Cho Jieun & Yang Chulmo), Natasha Myers, Jean-Luc Nancy & John Paul Ricco, Vincent Normand, Richard Pell & Emily Kutil, Tomás Saraceno, Sasha Engelmann & Bronislaw Szerszynski, Ada Smailbegovic, Karolina Sobecka, Zoe Todd, Richard Streitmatter-Tran & Vi Le, Anna-Sophie Springer, Sylvère Lotringer, Peter Sloterdijk, Etienne Turpin, Pinar Yoldas, and Una Chaudhuri, Fritz Ertl, Oliver Kellhammer & Marina Zurkow