Interactive Rule-based Specification with an Application to Visual Language Definition

In a rule-based approach the computation steps of a system are specified by rules that completely define how the system’s state may change. For open systems a more liberal approach is required, where the state changes are only partly specified, and – interactively – other com- ponents may contribute further information on how the transformation is defined completely. In this paper we introduce a formal model for in- teractive rule-based specifications, where states are modelled as partial algebras and transformations are given by internal algebra rewritings and arbitrary external components. As an application we discuss how visual languages can be defined in this framework. Thereby the internal (logical) representations of visual expressions are transformed by rewrit- ing rules, whereas their layouts are obtained interactively by external components like a constraint solver or a user working with a display and a mouse

A Coalgebraic presentation of structured transition systems

This paper relates labelled transition systems and coalgebras with the motivation of comparing and combining their complementary contributions to the theory of concurrent systems. The well-known mismatch between these two notions concerning the morphisms is resolved by extending the coalgebraic framework by lax cohomomorphisms. Enriching both labelled transition systems and coalgebras with algebraic structure for an algebraic specification, the correspondence is lost again. This motivates the introduction of lax coalgebras, where the coalgebra structure is given by a lax homomorphism. The resulting category of lax coalgebras and lax cohomomorphisms for a suitable endofunctor is shown to be isomorphic to the category of structured transition systems, where both states and transitions form algebras. The framework is also presented on a more abstract categorical level using monads and comonads, extending the bialgebraic approach introduced by Turi and Plotkin

Structured Transition Systems as Lax Coalgebras

This paper relates labeled transition systems and coalgebras with the motivation of comparing and combining their complementary contributions to the theory of concurrent systems. The well-known mismatch between these two notions for what concerns the morphisms is resolved by extending the coalgebraic framework by lax cohomomorphisms. Enriching both labeled transition systems and coalgebras with algebraic structure for an algebraic specification, the correspondence is lost again. This leads to the introduction of lax coalgebras, where the coalgebra structure is given by a lax homomorphism. The resulting category of lax coalgebras and lax cohomomorphisms for a suitable endofunctor is shown to be isomorphic to the category of structured transition systems, where both states and transitions form algebras. The framework is also presented on a more abstract categorical level using monads and comonads, extending the bialgebraic approach recently introduced by Turi and Plotkin

An Algebra of Graph Derivations Using Finite (co-) Limit Double Theories

Graph transformation systems have been introduced for the formal specication of software systems. States are thereby modeled as graphs, and computations as graph derivations according to the rules of the specication. Operations on graph derivations provide means to reason about the distribution and composition of computations. In this paper we discuss the development of an algebra of graph derivations as a descriptive model of graph transformation systems. For that purpose we use a categorical three level approach for the construction of models of computations based on structured transition systems. Categorically the algebra of graph derivations can then be characterized as a free double category with nite horizontal colimits. One of the main objectives of this paper is to show how we used algebraic techniques for the development of this formal model, in particular to obtain a clear and well structured theory. Thus it may be seen as a case study in theory design and its support by algebraic development techniques

Formal software specification with refinements and modules of typed graph transformation systems

Graph transformation systems are a formal specification technique for software systems that support the rule based specification of the dynamic behaviour of a system.Their main advantages are the intuitive visual representation of states and state transformations as graphs on the one hand, and the fully formal semantics on the other hand, that allow precise statements about the specification and tool support. In this paper we introduce refinements and modules for typed graph transformation systems to support the software specification development in both dimensions: modules for the horizontal structuring of a specification, i.e., its composition from feasible parts, and refinements for the development over time

Modeling Distributed Systems by Modular Graph Transformation based on Refinement via Rule Expressions

Due to the special requirements of distributed systems, it is important that modeling techniques for this kind of systems offer a stringent module concept. Each module has to support the encapsulation of data structure as well as functionality also at runtime. Modular graph transformation, presented in this contribution, supports these features. Modules are built up of specifications where attributed graphs describe the static data structures, whereas the dynamic behavior is modeled by the controlled application of graph rules. Rule expressions are used to formulate the control flow. Within one module, we can state a (weak) preservation of export and import behavior wrt. the local behavior in the module’s body in the sense that an interface derivation is subsumed by a local derivation if it can be performed. Modules may use each other meaning that each import interface has to be connected with an export interface in a way that the import behavior is subsumed by the export behavior

Transformation of combinded data type and process specifications using projection algebras

SIGLEAvailable from TIB Hannover: RN 2856(1990,1) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Differential change in integrative psychotherapy: A re-analysis of a change-factor based RCT in a naturalistic setting

General Psychotherapy (GPT; Grawe, 1997) is a research-informed psychotherapy that combines cognitive-behavioral and process-experiential techniques and that assumes motivational clarification and problem mastery as central mechanisms of change. To isolate the effect of motivational clarification, GPT was compared to a treatment that proscribed motivational clarification (General Psychotherapy Minus Clarification, GPT-C) in a randomized-controlled trial with 67 diagnostically heterogeneous outpatients. Previous analyses demonstrated equal outcomes and some superiority for highly avoidant patients in GPT. Re-analyses using causal-analytic methods confirmed equal changes, but also showed superior effects for GPT in highly symptomatic patients. Results are discussed regarding theory, methodological limitations, and implications for research and practice