17407466
Point-Based Approaches to Qualitative Temporal Reasoning
We are interested in the problem of qualitative, point-based temporal reasoning. That is, given a set of assertions concerning the relative positions of points in time, we are interested in compiling the assertions into a representation that supports efficient reasoning, determining consistency, computing the strongest entailed relation between any two points and updating the set of assertions. We begin by considering a general set of operations and their corresponding algorithms, applicable to general point-based temporal domains. We also consider special-purpose reasoners, which may be expected to perform well in an application domain with a restricted structure. Lastly we consider reasoners which incorporate restricted structures into a more general reasoning framework. Finally, we present instances of each such approach and give a comparison of their performance on random data sets.
204999323
Acyclic Directed Hypercubes may have Exponential Diameter
Abstract The diameter of a directed graph is the maximum of the lengths of the shortest paths between all pairs of vertices (if such paths exist). We prove that for every n , the edges of the n -dimensional hypercube can be acyclically oriented such that the diameter of the cube is F n + 1 , the ( n + 1)st Fibonacci number.
209133
Computing planar intertwines
The proof of Wagner's conjecture by N. Robertson and P. Seymour gives a finite description of any family of graphs which is closed under the minor ordering, called the obstructions of the family. Since the intersection and the union of two minor closed graph families are again a minor closed graph family, an interesting question is that of computing the obstructions of the new family given the obstructions for the original two families. It is easy to compute the obstructions of the intersection, but, until very recently, it was an open problem to compute the obstructions of the union. It is shown that if the original families are planar, then the obstructions of the union are no larger than n to the O(n/sup 2/) power, where n is the size of the largest obstruction of the original family.<<ETX>>
26737462
The Parallel Complexity of Tree Embedding Problems
Abstract The question of the sequential complexity of various tree embedding problems arises in the recent work of Robertson and Seymour on graph miners; here we consider the parallel complexity of such problems. In particular, we present two CREW PRAM algorithms: an O (log 3 n ) time randomized algorithm for determining whether there is a topological embedding of one rooted tree in another and an O (log 2 n log log n ) time deterministic algorithm for determining whether or not a rooted tree with a degree constraint is a minor of a general rooted tree. These algorithms are two examples of a general technique that can be used for solving other problems on trees.
28349058
A Constructive Proof that Trees Are Well-Quasi-Ordered Under Minors
The recent proof of Robertson and Seymour that graphs are well-quasi-ordered under minors immediately implies that a number of intesting problems have polynomial time algorithms. However, partially because of their non-constructive nature, these proofs do not yield any information about the algorithms. Here we present a constructive proof that trees are well-quasi-ordered under minors. This extends the results of Murty and Russell [MR90] who give a constructive proof of Higman's Lemma. Our proof is based on transforming finite sequences of trees to ordinals. We begin by describing a transformation which carries trees to finite strings of numbers and give an ordering on these strings which preserves the minor ordering on the underlying trees. We show that in our well-quasi-ordering argument, these strings are actually over a finite alphabet. This allows us to conclude the result. We require the well-ordering of the ordinal e0 for our proof.
17058061
Sequential and Parallel Algorithms for Embedding Problems on Classes of Partial k-Trees
We present sequential and parallel algorithms for various embedding problems on bounded degree partial k-trees and k-connected partial k-trees; these include subgraph isomorphism and topological embedding, known to be NP-complete for general partial k-trees. As well as contributing to our understanding of the types of graphs for which these problems are tractable, this paper introduces methods for solving problems on graphs. In particular, we make use of the tree-decomposition of the graph to apply techniques used to solve problems on trees to solve problems on partial k-trees.
25659803
BIRN-M: a semantic mediator for solving real-world neuroscience problems
A goal of the Biomedical Informatics Research Network (birn) project is to develop a multi-institution information management system for Neurosciences to gain a deeper understanding of several neurological disorders. Each institution specializes in a different subdiscipline and produces a database of its experimental or computationally derived data; a mediator module performs semantic integration over the databases to enable neuroscientists to perform analyses that could not be done from any single institution’s data. The overall system architecture of the birn system is that of a wrapper-mediator system. The information sources are various relational sources including Oracle 9i having userdefined packages, Oracle 8i with the Spatial Data Cartridge, and databases made available over the web. Sources also include computational resources that need to be “run” to produce data. A source can be either accessed directly by the mediator, or through a middleware called the Storage Resource Broker (SRB) to shield the mediator from keeping low-level information like data location and user authentication information, and from large object handling. Wrappers handle source registration, schema mapping, and translation from the mediator’s logic queries to the corresponding sql or web request. birn-m also admits knowledge sources, which host ontologies and domain-specific general knowledge in the form of logic rules. birn-m maintains a registry with semantic schemas from all sources, integrated views defined in a GAV fashion, and source query capabilities as binding patterns and special predicates or functions admissible by it. The registry also records the types of data a client can handle, and has an API for interactive custom-built clients.
18838099
Infrastructure Leasing Problems
Consider the following Steiner Tree leasing problem. Given a graph G= (V,E) with root r, and a sequence of terminal sets D t i¾? Vfor each day ti¾? [T]. A feasible solution to the problem is a set of edges E t for each tconnecting D t to r. Instead of obtaining edges for a single day at a time, or for infinitely long (both of which give Steiner tree problems), we leaseedges for say, { a day, a week, a month, a year}. Naturally, leasing an edge for a longer period costs less per unit of time. What is a good leasing strategy? In this paper, we give a general approach to solving a wide class of such problems by showing a close connection between deterministic leasing problems and problems in multistage stochastic optimization. All our results are in the offline setting.
16442037
Handwritten Bank Check Recognition Of Courtesy Amounts
In spite of rapid evolution of electronic techniques, a number of large-scale applications continue to rely on the use of paper as the dominant medium. This is especially true for processing of bank checks. This paper examines the issue of reading the numerical amount field. In the case of checks, the segmentation of unconstrained strings into individual digits is a challenging task because of connected and overlapping digits, broken digits, and digits that are physically connected to pieces of strokes from neighboring digits. The proposed architecture involves four stages: segmentation of the string into individual digits, normalization, recognition of each character using a neural network classifier, and syntactic verification. Overall, this paper highlights the importance of employing a hybrid architecture that incorporates multiple approaches to provide high recognition rates.
5331854
On the Scalable Computation of Large Sets of Integrals
We consider efficient strategies for the parallel and distributed computation of large sets of multivariate integrals. These arise in many applications such as computational chemistry, high energy physics and finite element problems. We use a hierarchical architecture which is highly scalable and allows parallelization not only at the domain level but also at the integral level. We present experimental results on a family of parametrized integrals and show that our approach leads to an efficient scalable load balanced algorithm. The methods are easily applicable to other areas where a large number of problems need to be solved efficiently on a parallel and distributed system.
32208794
Adaptive delivery of E-commerce web sites
Most e-commerce web sites are very large, often confusing and overwhelm the visitor with a huge amount of information. People cannot easily find what they are looking for. Moreover, the web site is presented in the same format to every visitor, irrespective of his needs. This paper proposes a model to solve the above problems. Our model divides the visitors into groups. Then it arranges web pages in the decreasing order of preference for each group and applies path prediction to find sink pages for that group. The results of these algorithms are displayed in a separate frame without modifying the site. Secondly, our paper addresses the need to guide visitors during the configuration of a product. We propose to apply data mining on the quotes for every group and find associations between different components of the product. We can then display these results as suggestions while the prospective buyer is configuring the product. These suggestions will dynamically change as each selection is made. We have discussed the data mining algorithms applicable to our model.