7434194
Multi-user support and motion planning of humans and humans driven vehicles in interactive 3D material flow simulations
The visualization of simulated production processes is used for their analysis. Huge plants are normally planned by a team. So a solution for many users who are modeling and interacting with a running model in an immersive 3D environment is required. We discuss an approach where several users work cooperatively on one simulation model. To optimize their work, the users need some guidance. For this we suggest small maps and arrows to guide the user to significant objects (machines). In many production scenarios, objects (forklifts, workers) are moving in an unguided fashion. In actual implementations these paths have to be modeled manually. In spite of taking these efforts, we are presenting an automated approach which is based on the 3D layout of the plant. If the user as part of the simulation is standing in the way of the object, the object stops in our approach (as hopefully in reality).
9204420
Partitioned neighborhood spanners of minimal outdegree
A geometric spanner with vertex set P IRD is a sparse approximation of the complete Euclidean graph determined by P. We introduce the notion of partitioned neighborhood graphs (PNGs), unifying and generalizing most constructions of spanners treated in literature. Two important parameters characterizing their properties are the outdegree k IN and the stretch factor f 1 describing the ‘quality’ of approximation. PNGs have been thuroughly investigated with respect to small values of f . We, on the other hand, present in this work results about feasable values of k — so to say the other extreme. The aim of minimizing this parameter rather than the first one arises from two observations: a) It determines the amount of space required for storing PNGs. b) Many algorithms employing a (previously constructed) spanner have running times depending on its outdegree. Our results include, for fixed dimensions D as well as asymptotically, upper and lower bounds on this optimal value of k. The upper bounds are constructive and yield efficient algorithms for actually computing the corresponding graphs. 1Partially supported by EU ESPRIT Long Term Research Project 20244 (ALCOM-IT) and DFG Grants Me872/7-1 and Me872/4-1
7656106
Geometric Searching in Walkthrough Animations with Weak Spanners in Real Time
We study algorithmic aspects in the management of geometric scenes in interactive walkthrough animations. We consider arbitrarily large scenes consisting of unit size balls. For a smooth navigation in the scene we have to fulfill hard real time requirements. Therefore, we need algorithms whose running time is independent of the total number of objects in the scene and that use as small space as possible. In this work we focus on one of the basic operations in our walkthrough system: reporting the objects around the visitor within a certain distance. 
 
Previously a randomized data structure was presented that supports reporting the balls around the visitor in an output sensitive time and allows insertion and deletion of objects nearly as fast as searching. These results were achieved by exploiting the fact that the visitor moves "slowly" through the scene. A serious disadvantage of the aforementioned data structure is a big space overhead and the use of randomization. 
 
Our first result is a construction of weak spanners that leads to an improvement of the space requirement of the previously known data structures. Then we develop a deterministic data structure for the searching problem in which insertion of objects are allowed. Our incremental data structure supports O(1+k) reporting time, where k is a certain quantity close to the number of reported objects. The insertion time is similar to the reporting time and the space is linear to the total number of objects.
14681345
The randomized sample tree: a data structure for interactive walkthroughs in externally stored virtual environments
We present a new data structure for rendering highly complex virtual environments of arbitrary topology. The special feature of our approach is that it allows an interactive navigation in very large scenes (30 GB/400 million polygons in our benchmark scenes) that cannot be stored in main memory, but only on a local or remote hard disk. Furthermore, it allows interactive rendering of substantially more complex scenes by instantiating objects.For the computation of an approximate image of the scene, a sampling technique is used. In the preprocessing, a so-called sample tree is built whose nodes contain randomly selected polygons from the scene. This tree only uses space that is linear in the number of polygons. In order to produce an image of the scene, the tree is traversed and polygons stored in the visited nodes are rendered. During the interactive walkthrough, parts of the sample tree are loaded from local or remote hard disk.We implemented our algorithm in a prototypical walkthrough system. Analysis and experiments show that the quality of our images is comparable to images computed by the conventional z-buffer algorithm regardless of the scene topology.
14377391
A Network Based Approach for Realtime Walkthrough of Massive Models
New dynamic search data structures developed recently guarantee constant execution time per search and update, i.e., they fulll the real-time requirements necessary for interactive walk-through in large geometric scenes. Yet, superiority or even applicability of these new methods in practice was still an open question. Their prototypical implementation presented in this work uses common libraries on standard workstations and thus represents a rst strut to bridge this gap. Indeed our experimental results give an indication on the actual performance of these theoretical ideas on real machines and possible bottlenecks in future developments. By special algorithmic enhancements, we can even avoid the otherwise essential preprocessing step.
2458859
Impossibility of distributed consensus with one faulty process
The consensus problem involves an asynchronous system of processes, some of which may be unreliable. The problem is for the reliable processes to agree on a binary value. We show that every protocol for this problem has the possibility of nontermination, even with only one faulty process. By way of contrast, solutions are known for the synchronous case, the "Byzantine Generals" problem.
1039321
A Support Tool for Writing Multilingual Instructions
Multilingual instructions generation has been the object of many studies recently, motivated by the increased need to produce multilingual manuals coupled with the cost of technical writing and translating. These studies concentrate on the automatic generation of instructions, leaving technical writers out of the loop. In many cases, however it is not possible to dispense with human intervention entirely, for at least two reasons. First, the system must be provided with a semantic knowledge base from which the instructions can be generated. Second, it is the technical writers who have the expertise necessary for producing instructions appropriate for a specific product or company, and it is not necessarily an easy task to make this expertise available to a system. The results of a requirement analysis study confirm the view that the most useful tool is not a stand-alone writing tool but rather one that supports technical writers in their task. In this paper, we describe such a support tool, which we developed based on the results of our user requirement analysis.
15236721
Bounds on secret key exchange using a random deal of cards
We present a general model for communication among a “team” of players overheard by a passive eavesdropper, Eve, in which all players including Eve are given private inputs that may be correlated. We define and explore secret key exchange in this model. Our secrecy requirements are information-theoretic and hold even if Eve is computationally unlimited. In particular, we consider the situation in which the team players are dealt hands of cards of prespecified sizes from a known deck of distinct cards. We explore when the team players can use the information contained in their hands to determine a value that each team player knows exactly but Eve cannot guess.
17113954
INTEGRATING ANTHROPOLOGICAL APPROACHES TO THE STUDY OF CULTURE: THE “HARD” AND THE “SOFT”
Much anthropological interest in methods derived from the natural sciences has been motivated by a search for tools with which to describe ethnographic settings in more “rigorous” terms. These have generally failed, and these failures are due to implicit conventions in anthropology regarding what to observe and how. I suggest that natural science methods were developed as a result of a process that aimed to solve problems that are generally different from those that social scientists pursue and that social scientists need to take the underlying ideas and rebuild them for their own purposes if they want to import them. Likewise, most qualitative anthropologists are also guilty of inappropriate borrowing, in particular in their importation of postmodern philosophy from literary criticism rather than adapting these ideas from the source in a manner more suited to the discipline. I examine some the conditions that would be necessary to integrate the various fractions of the anthropological community within a flexible but common framework. I conclude that anthropology must include a major qualitative perspective and, in response to this, suggest that if we are to formalize our study we must adopt some new conventions. These include a broadening of analysis beyond causality to include interpretive reasoning within a common framework, the addition of deontic operators to our basic formal framework, and an emphasis on declarative semantics over procedural semantics. We end by briefly describing some speculative work using Information Theory as a basis for quantitatively evaluating qualitative descriptions, models, and analysis.
62681368
Lambda-calculus schemata
A lambda-calculus schema is an expression of the lambda calculus augmented by uninterpreted constant and operator symbols. It is an abstraction of programming languages such as LISP which permit functions to be passed to and returned from other functions. When given an interpretation for its constant and operator symbols, certain schemata, calledlambda abstractions, naturally define partial functions over the domain of interpretation. Two implementation strategies are considered: the retention strategy in which all variable bindings are retained until no longer needed (implying the use of some sort of garbage-collected store) and the deletion strategy, modeled after the usual stack implementation of ALGOL 60, in which variable bindings are destroyed when control leaves the procedure (or block) in which they were created. Not all lambda abstractions evaluate correctly under the deletion strategy. Nevertheless, both strategies are equally powerful in the sense that any lambda abstraction can be mechanically translated into another that evaluates correctly under the deletion strategy and defines the same partial function over the domain of interpretation as the original. Proof is by translation into continuation-passing style.