Database Management and the Internet: Developments and Challenges - High-Performance Web Databases: Design, Development, and Deployment - page 547

are being examined to handle different data types. Once a standard language
has been developed, mappings between the standard language and the lan-
guages used by the individual databases must be examined.
For efficient query processing, modifications to current algorithms for
distributed and heterogeneous databases should be considered. For exam-
ple, current cost models focus mainly on the amount of data transferred
between the different sites. Database administrators have many issues to
consider, such as:
• Are such cost models still valid for Internet databases? Are there other
factors that need to be considered in query processing?
• Will the cost of accessing remote database servers over the Internet
have an impact on the query algorithms?
• What are the relationships between global and local optimization
strategies? What are parameters that are common to both the global
and local cost models?
Because of the information explosion caused by the Internet, various
technologies such as agents and mediators are being considered for locat-
ing the data sources, mediating between the different data sources, fusing
the data, and giving responses to the user.
Browsing and Filtering
Although many traditional DBMSs do not support browsing, such sys-
tems on the Internet need to provide this capability. One of the main uses
of the Internet is browsing through and accessing large amounts of infor-
mation in a short time. Therefore, to efficiently access the database, the
DBMS must be augmented by a browser. Numerous browsing tools are
available for the Internet, however, they must be integrated with the DBMS.
Closely related to browsing is the filtering technique. With the Internet, the
user can become overloaded with information. This means various filters
have to be integrated with the browsers and the DBMSs so that unnecessary
information is filtered out and users get only the information they want.
Transaction Management
Transaction management, an integral part of DBMSs, involves concur-
rency control and recovery. New kinds of transactions are taking place on
the Internet, such as making a purchase. In some cases, multiple users may
want to purchase the same item and may bid on it. In such a situation, there
should be a waiting period before the item is locked. The item is then sold
to the highest bidder.
The previous example illustrates the need for flexible transaction models.
The ability to perform long-duration transactions and transaction models for
workflow management may also be valuable. Serializability conditions may