: We describe a practical and enhanced implementation of a graphical Prolog tracer which not only provides a faithful (slow-motion) representation of the inner workings of the Prolog interpreter, but also allows a high-speed visual overview of execution for rapidly homing in on buggy code. The current work extends our original 'Transparent Prolog Machine' in the following ways: (a) complex unification histories for given variables can be displayed; (b) cross-variable dependencies (sharing) across widelydispersed sections of code can be highlighted; (c) an earlier defect, wherein a given user could write code which defeated the speed/size of the current fastest/largest display capability (i.e. a 'horizon effect') is dealt with; (d) users of textual (Byrd box) tracers are provided with an upward-compatible migration pathway; (e) code can be traced either 'live' or 'retrospectively' at different grains of detail. We distinguish among four different ways of manipulating the 'navigational s...

: Logic programs have traditionally been described by means of 'AND/OR' trees. The AORTA diagram is an And/OR Tree, Augmented to include invocation history 'status boxes' at each node. This augmentation makes it possible to present a graphical view of Prolog execution which is very compact, yet which contains complete details of unification and control history, including multiple (backtracking) invocations and extra-logical features such as the cut. The notation described herein serves as the uniform basis for textbook diagrams, video-based animations, and an advanced tracing and debugging facility running on modern graphics workstations. 1 Introduction For the past two years, we have been experimenting with ways of expressing the execution of Prolog programs in an easy-to-visualise manner. Our focus has been on producing an account of the language which is rich enough to satisfy the needs of experts, and has the descriptive power and clarity needed to teach difficult concepts to novi...

This technical report has been submitted as a dissertation to the faculty of the Department of Computer Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Graduate College of the University of Arizona

In the third act of Shakespeare's Hamlet, the hero is unsure whether to kill Claudius - the assassin of Hamlet's father - or not. He argues that if he does kill him, Claudius who is praying at that very moment goes to heaven and if he does not kill him Hamlet's father is not revenged. A contradiction. Ultima Ratio aims at formalization and visualization of argumentation for agents. An agent is constituted by a set of arguments and assumptions. Facing a particular world, the agent's believes may be inconsistent triggering a rational monologue to deal with the situation. Formally, we define a framework for argumentation based on extended logic programming under well-founded semantics. The system serves as decision support and is capable of detecting and removing contradictions and deriving conclusions of the agent's arguments. To demonstrate the structure and dynamics of the agent's argumentation, we visualise the process as dynamic construction of proof trees. The paper includes screenshots of the logical engine and the visualisation unit as exhibited at the computer arts exhibition Ars Electronica 98.

this paper is a means of significantly reducing the effort required to write a broad class of execution monitors

this paper, we describe a more intuitive approach to argumentation, which is based on its visualization

views of executions are the basis for a trace browser. 2.1 A trace query language based on Prolog We model an execution into a trace which is a stream of events. Execution events have a uniform representation, and can be analysed by programs. At a conceptual level, only two tracing primitives are necessary to retrieve trace information on the fly: one to retrieve the information related to the current event, another one to retrieve ? in, G. Comyn and N. Fuchs editors, Proceedings of the Second Logic Programming Summer School, September 1992, Zurich. Springer-Verlag, Lecture Notes in Artificial Intelligence 636. ??? Author's current address: IRISA/INSA, Campus Universitaire de Beaulieu, F-35042 Rennes, email: ducasse@irisa.fr information related to the next event. A trace can be considered as a history of execution events, and the two primitives can be matched on the notions of today (current event) and tomorrow (next event). These two primitives, plus Prolog, make a powerful tra...

An intelligible program diagram called Logichart has been developed for Prolog visualization. Its syntax rules and layout rules are formalized in terms of an attribute graph grammar. This grammar consists of a context--free graph grammar whose productions are defined in such a way as to formalize the graph--syntax rules of Logichart diagrams, and semantic rules which are defined in such a way that they can extract the layout information needed to display a Logichart diagram as attributes attached to node labels. Our Prolog visualization system implemented based on the attribute graph grammar can draw a Logichart diagram for any correct Prolog program (completeness) , and any Logichart diagram displayed by the system is always valid for the grammar (soundness). The system can also display the execution of a Prolog program in real time; that is, the Logichart diagram is dynamically updated as the program runs. 1 Introduction Prolog is a high--level, highly productive, programming langu...

ions in the Transparent Prolog Machine" 1 To appear in K. Bowen & R. Kowalski, (Eds.), Proceedings of the Fifth International Conference Symposium on Logic Programming. Cambridge, MA: MIT Press, 1988. ADDING DATA AND PROCEDURE ABSTRACTION TO THE TRANSPARENT PROLOG MACHINE (TPM) M. BRAYSHAW and M. EISENSTADT Human Cognition Research Laboratory The Open University Milton Keynes MK7 6AA, UK ABSTRACT The Transparent Prolog Machine (TPM) provides a vehicle for visualising the execution of Prolog programs in a manner which is faithful to the underlying behaviour of the Prolog interpreter. Although this fidelity is useful for teaching and debugging purposes, it can be inappropriate when a programmer wishes to view a program at a 'higher level', i.e. in terms of data or procedure abstractions which are not necessarily close to the underlying behaviour of the interpreter. We show how TPM can be extended to deal with the 'collection' abstraction inherent in higher-order predicates such as se...

In this paper, we give an account on visualisation of argumentation, agents, and arguing agents. We describe three scenarios above and discuss the advantages/disadvantages of our solution and compare it to alternative solutions.