Faculty Host: Dimitris Metaxas

Abstract:

A pictorial query specification technique that enables the formulation of complex pictorial queries for browsing through a collection of spatially-referenced images is presented. It is distinguished from most other methods by the fact that in these methods the query image specifies a target database image in its entirety whereas in our approach the query image specifies the combination of objects that the target database image should contain rather than being treated as a whole image. Using our technique, it is possible to specify which particular objects should appear in the target images, how many occurrences of each object are required, and spatial constraints that specify bounds on the distance between objects and the relative direction between them. Each pictorial query is composed of one or more query images. Each query image is constructed by selecting the required query objects and positioning them according to the desired spatial configuration. Boolean combinations of two or more query images are also possible by use of AND and OR operators. A query image may be negated in order to specify conditions that should not be satisfied by the database images that are retrieved successfully. In addition, a capability is provided to specify whether the same instance of an object is to be used when it appears in more than one of the query images that make up the pictorial query, or whether two different instances are allowed. Several example queries are given that demonstrate the expressive power of this query specification method in an application that browses the results in a map image database application.

* Joint work with Aya Soffer

Speaker Bio:

Hanan Samet received the B.S. degree in engineering from the University of California, Los Angeles, and the M.S. Degree in operations research and the M.S. and Ph.D. degrees in computer science from Stanford University, Stanford, CA. He is a Fellow of the IEEE, ACM, and IAPR (International Association for Pattern Recognition).

In 1975 he joined the Computer Science Department at the University of Maryland, College Park, where he is now a Professor. He is a member of the Computer Vision Laboratory of the Center for Automation Research and also has an appointment in the University of Maryland Institute for Advanced Computer Studies. At the Computer Vision Laboratory he leads a number of research projects on the use of hierarchical data structures for geographic information systems. His research group has developed the QUILT system which is a GIS based on hierarchical spatial data structures such as quadtrees and octree, the SAND system which integrates spatial and non-spatial data, the SAND Browser which enables browsing through a spatial database using a graphical user interface, the VASCO spatial indexing applet (found at http://www.cs.umd.edu/~hjs/quadtree/index.html), and a symbolic image database system.

His research interests are data structures, computer graphics, geographic information systems, computer vision, robotics, programming languages, artificial intelligence, and database management systems. He is the author of the books Design and Analysis of Spatial Data Structures, and Applications of Spatial Data Structures: Computer Graphics, Image Processing, and GIS, both published by Addison-Wesley, 1990.