Varol Akman

Steps toward Formalizing Context

The importance of contextual reasoning is emphasized by various researchers in AI. (A partial list includes John McCarthy and his group, R. V. Guha, Yoav Shoham, Giuseppe Attardi and Maria Simi, and Fausto Giunchiglia and his group.) Here, we survey the problem of formalizing context and explore what is needed for an acceptable account of this abstract notion.

The use of situation theory in context modeling

At the heart of natural language processing is the understanding of context dependent meanings. This paper presents a preliminary model of formal contexts based on situation theory. It also gives a worked‐out example to show the use of contexts in lifting, i.e., how propositions holding in a particular context transform when they are moved to another context. This is useful in NLP applications where preserving meaning is a desideratum.

Rethinking Context as a Social Construct

Abstract This paper argues that in addition to the familiar approach using formal contexts, there is now a need in artificial intelligence to study contexts as social constructs. As a successful example of the latter approach, I draw attention to ‘interpretation’ (in the sense of literary theory), viz, the reconstruction of the intended meaning of a literary text that takes into account the context in which the author assumed the reader would place the text. An important contribution here comes from Wendell Harris, enumerating the seven crucial dimensions of context: knowledge of reality, knowledge of language, and the authorial, generic, collective, specific, and textual dimensions. Finally, two recent approaches to interpretation, due to Jon Barwise and Jerry Hobbs, are analyzed as useful attempts which also come to grips with the notion of context. It must be noted that there has been a considerable body of contributions connecting linguistic structure with social context. For example, anthropological linguistics, from Bronislaw Malinowski onwards, has underlined the cultural context of discourse as essential to meaning. This viewpoint became prominent with the emergence of the ethnography of speaking in anthropology. Thus, conversation analysis represents a consistent formal effort to contribute to an analysis of the nature of context. While this paper emphasizes and reviews the literary theory approach, it makes various contacts with works of the latter kind (e.g., the landmark contributions of Erving Goffman, John Gumperz, William Hanks, John Heritage, Dell Hymes, et al.) in order to deliver a more balanced and complete study of the dimensions of context.

A fundamental and theoretical framework for an intelligent CAD system

Abstract Currently, there exists a line of research in mechanical CAD that is directed towards using AI and knowledge engineering ideas, but truly unifying approaches in this respect are lacking. The authors hope to fill this gap via a logic-based, theoretical approach. A formulation is given for how a designers apprentice (or a design workbench) can be established. The relevance of naive physics and commonsense reasoning in machine design are demonstrated. As for the software development methodology several aspects of software engineering are considered. A design base language which is built upon logic programming and object-oriented programming paradigm is proposed.

Geometric computing and uniform grid technique

If computational geometry should play an important role in the professional environment (e.g. graphics and robotics), the data structures it advocates should be readily implemented and the algorithms efficient. In the paper, the uniform grid and a diverse set of geometric algorithms that are all based on it, are reviewed. The technique, invented by the second author, is a flat, and thus non-hierarchical, grid whose resolution adapts to the data. It is especially suitable for telling efficiently which pairs of a large number of short edges intersect. Several of the algorithms presented here exist as working programs (among which is a visible surface program for polyhedra) and can handle large data sets (i.e. many thousands of geometric objects). Furthermore, the uniform grid is appropriate for parallel processing; the parallel implementation presented gives very good speed-up results.

Unobstructed shortest paths in polyhedral environments

Solution of the general instance of FINDPATH.- Solutions of two specific instances of FINDPATH.- Two Voronoi-based techniques for FINDPATH.- Desirable functionalities of a geometers workbench.- Conclusion and future work.

Efficiency of Uniform Grids for Intersection Detection on Serial and Parallel Machines

The uniform grid data structure is a flat (non-hierarchical) grid whose resolution adapts to the data. An exhaustive analysis of the uniform grid data structure for determining intersections in a set of many small line segments is presented. Databases from cartography, VLSI, and graphics with up to 115,973 edges are used. For each data set the intersection time, the ratio of edge pairs tested to pairs found to intersect, and size of intermediate data structures was measured as a function of grid resolution. The execution time was relatively insensitive to the grid size over a range of up to a factor of 10. 115,973 edges were processed to find 135,050 intersections in 683 seconds on a Sun 3/50 workstation. This data structure is also ideally suited for implementation on a parallel machine. When executing on a 16 processor Sequent Balance 21000, total times averaged ten times faster than when using only one processor. Finding all 81,373 intersections in a 62,045 edge database took only 28 seconds elapsed time. This research shows that more complicated, hierarchical data structures, such as quadtrees, are not necessary for this problem.

Current Approaches to Punctuation in Computational Linguistics

Some recent studies in computational linguistics have aimed to take advantage of various cues presented by punctuation marks. This short survey is intended to summarise these research efforts and additionally, to outline a current perspective for the usage and functions of punctuation marks. We conclude by presenting an information-based framework for punctuation, influenced by treatments of several related phenomena in computational linguistics.Varol Akman is a professor of computer engineering at Bilkent University, Ankara, Turkey. From 1980 to 1985, he was a Fulbright scholar at Rensselaer Polytechnic Institute, Troy, New York, where he received a PhD degree in computer engineering. Prior to joining Bilkent in 1988, he held a senior researcher position with the Centrum voor Wiskunde en Informatica, Amsterdam, the Netherlands. His current research areas include artificial intelligence models of context, computational aspects of situation theory, and in general, language and philosophy.

Sweeping with all graphical ingredients in a topological picturebook

Abstract Sweeping is a powerful method to generate 3-D shapes in geometric modeling. In this paper we formulate a general matrix to give a mathematical definition of twisted-profiled sweep objects as a discrete approximation. While conceptually simple, our result is, to our best knowledge, the first precise formulation of sweeping with all graphical ingredients, viz. twisting, scaling, rotation, and translation. Twisted-profiled sweeping surfaces defined by contour, profile, trajectory, and guide curves are thus represented in concatenated matrix formulation. In addition, we give interactive methods to generate sweep objects and present sample figures produced within the framework of our implementation Tb, a topological picturebook.

The complexity of context: guest editors’ introduction☆

As with other widely used notions that are commonly referred to in everyday activities without much hesitation, context is difficult to analyze scientifically and grasp in all its different demeanors. In our routine communicative activities, context is exploited both in production and in comprehension, and is strictly related to another problematic notion, viz. meaning. Thus Bateson (1979: 15): ‘‘Without context, words and actions have no meaning at all. This is true not only of human communication in words but also of all communication whatsoever, of all mental process, of all mind, including that which tells the sea anemone how to grow and the amoeba what he should do next.’’ Journal of Pragmatics 35 (2003) 321–329 www.elsevier.com/locate/pragma