205118584
dI-Domains as Prime Information Systems
Abstract This paper introduces prime information systems. Prime information systems determine dI-domains and stable approximable mappings give stable functions, and vice versa. The notion of rigid embedding is captured by a subsystem relation. Under this relation, prime information systems form a complete partial order (cpo). Constructions like lifting, sum, product, and function space are proposed which induce continuous functions on the cpo. In this way recursive prime information systems can be defined using fixed point theory.
43741261
Parallel Product of Event Structures
Event structures were introduced by Nielsen, Plotkin and Winskel [5] as a model for computational processes. These were essentially sets of events with relations expressing causal dependence and conflicts between them. These structures, also called prime event structures, were shown to be connected both with a class of acyclic Petri nets (called by the authors occurrence nets) and with a class of domains (finitary prime algebraic coherent domains). Though a very pleasant model of computation, prime event structures can lead to tedious definitions for more sophisticated constructions such as parallel product or exponentiation. In subsequent papers [8,9], Winskel introduced a more general class of event structures called stable event structures, for which such constructions are defined categorically. Although stable event structures themselves are slightly more complicated than prime event structures, constructions on them can be defined in an elegant way. In general, category theory has proven very useful for computer science. When constructions are formulated in categorical terms, not only can the required universal properties provide some guideline in the definitions, the associated morphisms may contain suggestions of computational interest as well. Moving to more general structures, however, can sometimes shield the intuitions about the model. In the case of stable event structures, the causality relation on events is not explicitly given, but is derived from an enabling relation on events. This makes such event structures a little hard to visualize, and one may wonder whether a more manageable notion could be devised. Moreover, unlike prime event structures, it is not clear if stable event structures correspond to a class of Petri nets, in the sense of [5]. Flow event structures were proposed in [2] as an intermediate between prime event structures and stable event structures, suitable both for graphical representation and for an easy definition of process operators. Among these operators the critical one is the
16175403
A modal logic for reasoning about belief
The purpose of this paper is to integrate a number of ideas from knowledge representation, with ideas from the semantics of programming language, in a basic logical system for belief. A knowledge-based system can be considered as, in a simplified way, an agent which, based on its current state of information, reasons for purposes such as planning or taking an action that best suits the agent's goal. There are different ways to formalize such a system. The approach we are taking is model checking: we express an agent's current state of knowledge by a semantic model, and the agent's belief or action as some logical formulas. The paradigm of model checking deals with the issue of whether an agent's current state of knowledge supports an action or a belief. Only supported belief or action are considered as appropriate. This paradigm is, in particular, different from the traditional logical one which represents an agent's state of knowledge by a set of first-order formulas, and considers a belief or an action appropriate if it happens to be a logical consequence of the set of given formulas.
11563132
Weakly Distributive Domains
In our previous work [17] we have shown that for any ω-algebraic meet-cpo D, if all higher-order stable function spaces built from D are ω-algebraic, then D is finitary. This accomplishes the first of a possible, two-step process in solving the problem raised in [1,2]: whether the category of stable bifinite domains of Amadio-Droste-Gobel [1,6] is the largest cartesian closed full sub-category within the category of ω-algebraic meet-cpos with stable functions. This paper presents results on the second step, which is to show that for any ω-algebraic meet-cpo D satisfying axioms M and | to be contained in a cartesian closed full sub-category using ω-algebraic meet-cpos with stable functions, it must not violate MI∞. We introduce a new class of domains called weakly distributive domains and show that for these domains to be in a cartesian closed category using ω-algebraic meet-cpos, property MI∞ must not be violated. We further demonstrate that principally distributive domains (those for which each principle ideal is distributive) form a proper subclass of weakly distributive domains, and Birkhoff's M3 and N5 [5] are weakly distributive (but non-distributive). We introduce also the notion of meet-generators in constructing stable functions and show that if an ω-algebraic meet-cpo D contains an infinite number of meet-generators, then [D → D] fails I. However, the original problem of Amadio and Curien remains open.
1726106
Defaults in Domain Theory
Abstract This paper uses ideas from artificial intelligence to show how default notions can be defined over Scott domains. We combine these ideas with ideas arising in domain theory to shed some light on the properties of nonmonotonicity in a general model-theoretic setting. We consider in particular a notion of default nonmonotonic entailment between prime open sets in the Scott topology of a domain. We investigate in what ways this notion obeys the so-called laws of cautious monotony and cautious cut , proposed by Gabbay, Kraus, Lehmann, and Magidor. Our notion of nonmonotonic entailment does not necessarily satisfy cautious monotony, but does satisfy cautious cut. In fact, we show that any reasonable notion of nonmonotonic entailment on prime opens over a Scott domain, satisfying in particular the law of cautious cut, can be concretely represented using our notion of default entailment. We also give a variety of sufficient conditions for defaults to induce cumulative entailments, those satisfying cautious monotony. In particular, we show that defaults with unique extensions are a representation of cumulative nonmonotonic entailment. Furthermore, a simple characterization is given for those default sets which determine unique extensions in coherent domains. Finally, a characterization is given for Scott domains in which default entailment must be cumulative. This is the class of daisy domains ; it is shown to be cartesian closed, a purely domain-theoretic result.
14387948
Axiomatic Aspects of Default Inference
This paper studies axioms for nonmonotonic consequences from a semantics-based point of view, focusing on a class of mathematical structures for reasoning about partial information without a predefined syntax/logic. This structure is called a default structure. We study axioms for the nonmonotonic consequence relation derived from extensions as in Reiter's default logic, using skeptical reasoning, but extensions are now used for the construction of possible worlds in a default information structure. 
In previous work we showed that skeptical reasoning arising from default-extensions obeys a well-behaved set of axioms including the axiom of cautious cut. We show here that, remarkably, the converse is also true: any consequence relation obeying this set of axioms can be represented as one constructed from skeptical reasoning. We provide representation theorems to relate axioms for nonmonotonic consequence relation and properties about extensions, and provide one-to-one correspondence between nonmonotonic systems which satisfies the law of cautious monotony and default structures with unique extensions. Our results give a theoretical justification for a set of basic rules governing the update of nonmonotonic knowledge bases, demonstrating the derivation of them from the more concrete and primitive construction of extensions. It is also striking to note that proofs of the representation theorems show that only shallow extensions are necessary, in the sense that the number of iterations needed to achieve an extension is at most three. All of these developments are made possible by taking a more liberal view of consistency: consistency is a user defined predicate, satisfying some basic properties.
13849872
As-consistent-As-possible compositing of virtual objects and video sequences
We present an efficient approach that merges the virtual objects into video sequences taken by a freely moving camera in a realistic manner. The composition is visually and geometrically consistent through three main steps. First, a robust camera tracking algorithm based on key frames is proposed, which precisely recovers the focal length with a novel multi-frame strategy. Next, the concerned 3D models of the real scenes are reconstructed by means of an extended multi-baseline algorithm. Finally, the virtual objects in the form of 3D models are integrated into the real scenes, with special cares on the interaction consistency including shadow casting, occlusions, and object animation. A variety of experiments have been implemented, which demonstrate the robustness and efficiency of our approach. Copyright © 2006 John Wiley & Sons, Ltd.
7914535
Stereoscopic Video Synthesis from a Monocular Video
This paper presents an automatic and robust approach to synthesize stereoscopic videos from ordinary monocular videos acquired by commodity video cameras. Instead of recovering the depth map, the proposed method synthesizes the binocular parallax in stereoscopic video directly from the motion parallax in monocular video, The synthesis is formulated as an optimization problem via introducing a cost function of the stereoscopic effects, the similarity, and the smoothness constraints. The optimization selects the most suitable frames in the input video for generating the stereoscopic video frames. With the optimized selection, convincing and smooth stereoscopic video can be synthesized even by simple constant-depth warping. No user interaction is required. We demonstrate the visually plausible results obtained given the input clips acquired by ordinary handheld video camera.
2928763
GeoGrid: A Scalable Location Service Network
This paper presents GeoGrid, a geographical location service overlay network system, for providing scalable location-based services to a large and growing number of mobile users. GeoGrid is designed as a decentralized and geographical location aware overlay network and provides system-level facilities and optimizations for balancing load in the presence of node heterogeneity, dynamically moving hot-spots (location queries), and unpredictable rate of node join, departure and failure. GeoGrid uses geographical mapping of nodes to regions and geographical proximity based routing to take advantage of the similarity between physical and network proximity. Furthermore, GeoGrid exploits multiple opportunities for dynamic workload adaptation in the presence of static hotspot queries and moving hotspot queries. Its dynamic load balancing algorithms can efficiently utilize the heterogeneous capacities of end systems and balance both the location query workload and the routing workload. Our initial prototype development and experimental study demonstrate that GeoGrid can effectively reduce the workload imbalance by an order of magnitude.
7172030
Information-theoretic inequalities for contoured probability distributions
We show that for a special class of probability distributions that we call contoured distributions, information-theoretic invariants and inequalities are equivalent to geometric invariants and inequalities of bodies in Euclidean space associated with the distributions. Using this, we obtain characterizations of contoured distributions with extremal Shannon and Renyi entropy. We also obtain a new reverse information-theoretic inequality for contoured distributions.
42909091
Combining path relinking and genetic algorithms for the multiple-level warehouse layout problem
Path relinking is a method to generate new solution by exploring trajectories that connect high quality solutions. In this paper, a class of new hybrid heuristics are proposed by combining a genetic algorithm and path relinking and applying these to a multiple-level warehouse layout problem. Parallel and series combinations to integrate crossover and mutation operations of a genetic algorithm with path relinking are investigated. We proposed position and sequence based path relinking methods to connect two solutions, which are either elites or ones selected randomly. Extensive experiments are carried out to compare the performance of the new heuristics.