Amalia -- A Unified Platform for Parsing and Generation

Contemporary linguistic theories (in particular, HPSG) are declarative in nature: they specify constraints on permissible structures, not how such structures are to be computed. Grammars designed under such theories are, therefore, suitable for both parsing and generation. However, practical implementations of such theories don't usually support bidirectional processing of grammars. We present a grammar development system that includes a compiler of grammars (for parsing and generation) to abstract machine instructions, and an interpreter for the abstract machine language. The generation compiler inverts input grammars (designed for parsing) to a form more suitable for generation. The compiled grammars are then executed by the interpreter using one control strategy, regardless of whether the grammar is the original or the inverted version. We thus obtain a unified, efficient platform for developing reversible grammars.Comment: 8 pages postscrip

An Investigation of Abadi and Cardelli's Untyped Calculus of Objects

We study the relationship between the natural (big-step) semantics and the reduction (small-step) semantics of Abadi and Cardelli's untyped calculus of objects. By applying Danvy et al.'s functional correspondence to the natural semantics, we derive an abstract machine for this calculus, and by applying Danvy et al.'s syntactic correspondence to the reduction semantics, we also derive an abstract machines for this calculus. These two abstract machines are identical. The fact that the machines are identical, and the fact that they have been derived using meaning-preserving program transformations, entail that the derivation constitutes a proof of equivalence between natural semantics and the reduction semantics. The derivational nature of our proof contrasts with Abadi and Cardelli's soundness proof, which was carried out by pen and paper. We also note that the abstract machine is new. To move closer to actual language implementations, we reformulate the calculus to use explicit substitutions. The reformulated calculus is new. By applying the functional and syntactic correspondences to natural and reduction semantics of this new calculus, we again obtain two abstract machines. These two machines are also identical, and as such, they establish the equivalence of the natural semantics and the reduction semantics of the new calculus. Finally, we prove that the two abstract machines are strongly bisimilar. Therefore, the two calculi are computationally equivalent

Programmiersprachen und Rechenkonzepte

Seit 1984 veranstaltet die GI-Fachgruppe "Programmiersprachen und Rechenkonzepte" regelmäßig im Frühjahr einen Workshop im Physikzentrum Bad Honnef. Das Treffen dient in erster Linie dem gegenseitigen Kennenlernen, dem Erfahrungsaustausch, der Diskussion und der Vertiefung gegenseitiger Kontakte. In diesem Forum werden Vorträge und Demonstrationen sowohl bereits abgeschlossener als auch noch laufender Arbeiten vorgestellt, unter anderem (aber nicht ausschließlich) zu Themen wie - Sprachen, Sprachparadigmen - Korrektheit von Entwurf und Implementierung - Werkzeuge - Software-/Hardware-Architekturen - Spezifikation, Entwurf - Validierung, Verifikation - Implementierung, Integration - Sicherheit (Safety und Security) - eingebettete Systeme - hardware-nahe Programmierung. In diesem Technischen Bericht sind einige der präsentierten Arbeiten zusammen gestellt

ContextWorkflow: A Monadic DSL for Compensable and Interruptible Executions

Context-aware applications, whose behavior reactively depends on the time-varying status of the surrounding environment - such as network connection, battery level, and sensors - are getting more and more pervasive and important. The term "context-awareness" usually suggests prompt reactions to context changes: as the context change signals that the current execution cannot be continued, the application should immediately abort its execution, possibly does some clean-up tasks, and suspend until the context allows it to restart. Interruptions, or asynchronous exceptions, are useful to achieve context-awareness. It is, however, difficult to program with interruptions in a compositional way in most programming languages because their support is too primitive, relying on synchronous exception handling mechanism such as try-catch. We propose a new domain-specific language ContextWorkflow for interruptible programs as a solution to the problem. A basic unit of an interruptible program is a workflow, i.e., a sequence of atomic computations accompanied with compensation actions. The uniqueness of ContextWorkflow is that, during its execution, a workflow keeps watching the context between atomic actions and decides if the computation should be continued, aborted, or suspended. Our contribution of this paper is as follows; (1) the design of a workflow-like language with asynchronous interruption, checkpointing, sub-workflows and suspension; (2) a formal semantics of the core language; (3) a monadic interpreter corresponding to the semantics; and (4) its concrete implementation as an embedded domain-specific language in Scala

Bridging the gap: building better tools for game development

The following thesis is about questioning how we design game making tools, and how developers may build easier tools to use. It is about the highlighting the inadequacies of current game making programs as well as introducing Goal-Oriented Design as a possible solution. It is also about the processes of digital product development, and reflecting on the necessity for both design and development methods to work cohesively for meaningful results. Interaction Design is in essence the abstracting of key relations that matter to the contextual environment. The result of attempting to tie the Interaction Design principles, Game Design issues together with Software Development practices has led to the production of the User-Centred game engine, PlayBoard

METHODS OF CHECKING AND USING SAFETY CRITERIA

This article describes methods and tools for automated safety analysis of UML statechart specifications. The general safety criteria described in the literature are reviewed, updated and applied for using in automated specification completeness and consistency analysis of object-oriented specifications. These techniques are proposed and based on OCL expressions, graph transformations and reachability analysis. To help the checking intermediate representations will be introduced. For using these forms, the correctness and completeness of checker methods can be proven. For the non-checkable criteria two constructive methods are proposed. They use design patterns and OCL expressions to enforce observation of the safety criteria. The usability and the rules of using will be also discussed. Three real systems have been checked by using these methods