Information Technology Reference
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synchronous processing, this also facilities the development of synchronous
messaging solutions over asynchronous messaging solutions.
When speaking of middleware products, we encompass a large variety of
technologies. The most common forms of middleware are as follows:
1. Database access technologies
2. Asynchronous Middleware
3. Synchronous Middleware
4. Message-oriented Middleware
5. Request/Reply Messaging Middleware
6. Transaction Processing Monitors
7. Object Request Brokers
8. Application Servers
9. Web Services
10. Enterprise Service Buses
11. Enterprise Systems
We discuss these in detail in the following sections.
5.2 Database Access Technologies
Database access technologies provide access to the database through
an abstraction layer, which enables us to change the actual Database
Management System (DBMS) without modifying the application source code.
In other words, it enables us to use the same or similar code to access differ-
ent database sources. Therefore, database access technologies are useful for
extracting data from different DBMSs. The technologies differ in the form
of interfaces to the database they provide. They can offer function-oriented
or object-oriented access to databases. The best known representatives are
Java Database Connectivity (JDBC) and Java Data Objects (JDO) on the Java
platform and Open Database Connectivity (ODBC) and Active Data Objects
(ADO.NET) on the Microsoft platform.
To expose data to the outside world, data source applications (i.e., data-
bases) could incorporate a standard-based data access component for a
remote application to perform functions on the database. The generic name
for this type of standard is call level interface (CLI). The concept of CLI was
originally created by the Structured Query Language (SQL) Access Group,
an industry group created to define industry SQL standards. CLI shields
the developer from the individual database. As long as the database is CLI
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