ABSTRACT
DURING RECENT MONTHS THERE HAS BEEN AN INCREASING DEMAND TO access the data stored in different databases through the Internet. The databases may be relational databases, object-oriented databases, or multimedia databases containing unstructured and semistructured data such as text, voice, video, and images. These databases are often heterogeneous in nature. Heterogeneity exists with respect to data structures, data types, semantic meanings, data models, architectures, query processing strategies, and transaction management techniques.
