Invisible Actions Research Articles

Weak Bisimulation for Action-Type Coalgebras: (Extended Abstract)

We propose a coalgebraic definition of weak bisimulation for a class of coalgebras obtained from bifunctors over the category Set. Weak bisimilarity for a system is obtained as strong bisimilarity of a transformed system. The transformation consists of two steps: First, the behaviour on actions is expanded to behaviour on finite words. Second, the behaviour on finite words is taken modulo the hiding of invisible actions, yielding behaviour on equivalence classes of words closed under silent steps. The coalgebraic definition is justified by two correspondence results, one for the classical notion of weak bisimulation of Milner and another for the notion of weak bisimulation for generative probabilistic transition systems as advocated by Baier and Hermanns.

Visual motion priming by invisible actions

Element shape biases the perceived direction in ambiguous apparent motion displays. Likewise, the direction of motion influences the perception of ambiguous elements’ shapes. A recent framework that suggests common spatial representations for perception and action predicts that actions should also influence the perceived direction of motion in ambiguous displays. In four experiments the perceived direction of an ambiguous display was shown to be primed by different types of invisible actions. An investigation of several aspects of action processing (like the type and direction of the hand movement or direction of the cue for the hand movement) showed that priming only occurred if the goal of the action and the motion display shared a common cognitive dimension. When that common dimension is given, planning an action is sufficient for motion priming.

The Corporeal Stenographer: Language, Gesture, and Cyberspace

The author describes her research and creative practice exploring the intersection between digital, biomedical, and linguistic modes of bodi ly representation. She synthesizes traditional forms of painting with new computer and medical imaging technologies to call into question the relationship between visible and invisible bodily forms and actions. Her paintings and installations use scientifically rendered images of the body (from symbolic DNA sequences to developing cel lular structures) in order to consider the role of the tools and technologies used to organize and view these images. The issue of visual, linguistic, and scientific literacy is thus a corollary concern.

Testing Equivalence for Mobile Processes

The impact of applying the testing approach to a calculus of processes with dynamic communication topology is investigated. A proof system is introduced that consists of two groups of laws: those for strong observational equivalence and those needed to deal with invisible actions. Soundness and completeness of this proof system w.r.t. a testing preorder are shown. A fully abstract denotational model for the language is presented that takes advantage of reductions of processes to normal forms.

Maximality preserving bisimulation

A new bisimulation notion is introduced for the specification of concurrent systems, which resists to a large class of action refinements, even in the presence of invisible actions. The work is presented in the context of labelled P/T nets, but it may be transported to other popular frameworks like prime event structures, process graphs, etc.

On the space cost curve and industrial location: Comment

We propose a coalgebraic definition of weak bisimulation for classes of coalgebras obtained from bifunctors in the category Set. Weak bisimilarity for a system is obtained as strong bisimilarity of a transformed system. The particular transformation consists of two steps: First, the behavior on actions is lifted to behavior on finite words. Second, the behavior on finite words is taken modulo the hiding of internal or invisible actions, yielding behavior on equivalence classes of words closed under silent steps. The coalgebraic definition is validated by two correspondence results: one for the classical notion of weak bisimulation of Milner, another for the notion of weak bisimulation for generative probabilistic transition systems as advocated by Baier and Hermanns.