or example, if you are looking for words in long strings of text, you could use a table accessed by indices that are functions of individual words. The table contains the strings where the word appears and the location of the word in the strings. It would be easy then to locate a word by retrieving all of its appearances from the table. This kind of approach was originally proposed for geometric object recognition, making use of indices based on local geometric features that remained invariant to the object transformation. The features were local to handle partial occlusion, and their indexing function was invariant to the relevant transformation, because unlike words in text, geometric features have both location and orientation. For over a decade now, indexing-based approaches have been gaining ground as the method of choice for building working recognition systems that can Geometric Hashing: An Overview HAIM J. WOLFSON Tel Aviv

In an object recognition system, if the extracted image features are multilevel or multiscale, the indexing structure may take the form of a tree. Such structures are not only common in computer vision, but also appear in linguistics, graphics, computational biology, and a wide range of other domains. In this paper, we develop an indexing mechanism that maps the topological structure of a tree into a low-dimensional vector space. Based on a novel eigenvalue characterization of a tree, this topological signature allows us to efficiently retrieve a small set of candidates from a database of models. To accommodate occlusion and local deformation, local evidence is accumulated in each of the tree's topological subspaces. We demonstrate the approach with a series of indexing experiments in the domain of 2-D object recognition. 1 Introduction In an object recognition system, indexing is the process by which a collection of one or more extracted image features belonging to an object is used...

Hierarchical image structures are abundant in computer vision and have been used to encode part structure, scale spaces, and a variety of multiresolution features. In this paper, we describe a framework for indexing such representations that embeds the topological structure of a directed acyclic graph (DAG) into a low-dimensional vector space. Based on a novel spectral characterization of a DAG, this topological signature allows us to efficiently retrieve a promising set of candidates from a database of models using a simple nearest-neighbor search. We establish the insensitivity of the signature to minor perturbation of graph structure due to noise, occlusion, or node split/merge. To accommodate large-scale occlusion, the DAG rooted at each nonleaf node of the query "votes" for model objects that share that "part," effectively accumulating local evidence in a model DAG's topological subspaces. We demonstrate the approach with a series of indexing experiments in the domain of view-based 3D object recognition using shock graphs.

In Pattern Recognition, the Graph Matching problem involves the matching of a sample data graph with the subgraph of a larger model graph where vertices and edges correspond to pattern parts and their relations. In this paper, we present Rulegraphs, a new method that combines the Graph Matching approach with Rule-Based approaches from Machine Learning. This new method reduces the cardinality of the (NP-Complete) Graph Matching problem by replacing model part, and their relational, attribute states by rules which depict attribute bounds and evidence for di erent classes. We show how rulegraphs, when combined with techniques for checking feature label-compatibilities, not only reduce the search space but also improve the uniqueness of the matching process.

We address the problem of obtaining natural (intuitive) descriptions of 3D shapes. We present one of the first attempts to address the description of 3D compound objects, where the parts are connected smoothly. The input we consider is either complete 3D data or range data from a single view. We suggest a volumetric graph representation of the object, where the nodes represent individual parts and the edges represent connectivity information. We suggest the use of properties of the parabolic curves for performing the part decomposition. We currently consider parts with tubular structure with a straight or curved axis. The graph description presents a structural description of the shape in terms of parts and their arrangement. We are also interested in the internal description of the parts. We study two well defined classes of shapes, namely Straight Homogeneous Generalized Cylinders, and Planar Right Constant GCs. We suggest the use of properties of the parabolic curves for recovering natural descriptions of these classes in terms of their cross sections and axes. 1

And then the man steps right up to the microphone And says at last as the time bell rings ``Thank you good night now it's time to go home'' and he makes it fast with one more thing ``We are the Sultans of Swing''

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Today's computer vision applications often have to deal with multiple, uncertain, and incomplete visual information. In this paper, we apply a new method, termed `active fusion', to the problem of generic object recognition. Active fusion provides a common framework for active selection and combination of information from multiple sources in order to arrive at a reliable result at reasonable costs. In our experimental setup we use a camera mounted on a 2m x 1.5m x/z-table observing objects placed on a rotating table. Zoom, pan, tilt and aperture setting of the camera can be controlled by the system. We follow a part-based approach, trying to decompose objects into parts, which are modeled as geons. The active fusion system starts from an initial view of the objects placed on the table and is continuously trying to refine its current object hypotheses by requesting additional views. The implementation of active fusion on the basis of probability theory, Dempster-Shafer's theory of evide...

Abstract-This paper deals with enhancing the level of autonomy in a robotic work cell. With that mission in mind, we present here an integrated framework for the sensing, the planning, and the execution aspects of assembly. In experimental demonstrations of this system on a PUMA762, we can now throw objects randomly into the workspace of the robot and the robot then automatically synthesizes a manipulation plan that includes the operations of sensing, grasping, and regrasping. Each operation is invoked only when it is deemed necessary for the successful execution of assembly. I.

Technical University. During my visit, a graduate student was kind enough to show me around Prague, including a visit to the Museum of Modern and Contemporary Art (Veletr˘zní Palác). It was there that I saw the sculpture