Efficient Storage and Delivery of Images for the Digital Library
                 
                       Oscar H. Ibarra
                Department of Computer Science
                  University of California
               Santa Barbara, California 93106


We give a brief overview of the Alexandria Digital Library (ADL)
project at the University of California at Santa Barbara.  ADL's
emphasis is on spatial data and images.  In an image browsing
environment such as the ADL's, there is need for a design that
allows viewing image subregions in progressively higher resolutions.
We describe a storage scheme that accomplishes good image compression,
while providing fast image subregion retrieval at various resolutions.
This storage scheme is applied on the quantized coefficient matrices
obtained from the application of wavelet transforms to images.  Our
encoding algorithm uses quadtrees to provide good compression and
efficient region indexing, coupled with Huffman coding to further
improve the compression ratios.  We also briefly describe our work on
a multiprocessor server that provides scalable WWW access to ADL images. 



Oscar H. Ibarra received the B.S. degree in Electrical Engineering from
the University of the Philippines in 1962 and the M.S. and Ph.D. degrees,
also in Electrical Engineering, from the University of California, Berkeley,
in 1965 and 1967, respectively.  He is currently a Professor of Computer
Science at the University of California, Santa Barbara.  He has previously
been with the faculties of UC Berkeley (1967-1969) and the University of
Minnesota (1969-1990).  Dr. Ibarra's research interests include the design
and analysis of algorithms, the theory of computation, computational
complexity, and parallel computing.  He is a Fellow of the Association for
Computing Machinery (ACM), the Institute of Electrical and Electronics
Engineers (IEEE), the American Association for the Advancement of Science
(AAAS), and the Minnesota Supercomputer Institute.  He is a recipient of
a Guggenheim Fellowship.

Dr. Ibarra is on the editorial boards of IEEE Transactions on Parallel and
Distributed Systems, Journal of Parallel and Distributed Computing,
Theoretical Computer Science, International Journal of Foundations of Computer
Science, Journal of Computing and Information, and Journal of VLSI Signal
Processing.  He was on the editorial board of IEEE Transactions on Computers
from 1991-1994.  He is on the advisory board of the Parallel Computing Book
Series for Chapman and Hall.