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<h1>Data Persistence</h1><p>Software programs using different data
persistence technologies are an integral part of contemporary informational
space. More than often such systems are implemented with the help of
object-oriented programming language (Java, c#, etc.) and a relational database
management system (Oracle, MySQL, etc.). This implementation originally
contains a mismatch between relational and object worlds, which is often called
"object/relational impedance mismatch" (OR mismatch shortly). The
essence of the problem is in the way the systems are designed. Object systems
consist of objects and are characterized by identity, state, behavior,
encapsulation. The relational model consists of tables, columns, rows and
foreign keys and is described by relation, attribute, tuple, relation value and
relation variable.</p>
<p>The object-relational mismatch has become
enormously significant with the total adoption of OO technology. This resulted
in the rapid development of so-called object-relational mappers (ORM), such as
Hibernate or Toplink. This solution "cures" the symptoms of the OR
mismatch by adding a layer into the software stack that automates the tedious
task of linking objects to tables. However, this approach creates a huge drain
on system performance, drives up software complexity, and increases the burden
on software maintenance, thus resulting in higher cost of ownership. While the
mapper solution may be feasible in large, administered datacenter environments,
it is prohibitive in distributed and zero-administration architectures such as
those required for embedded databases in client software, mobile devices,
middleware or real-time systems.</p>
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This revision (1) was last Modified 2007-05-03T10:50:02 by Tetyana.
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