A DBMS must provide support for the storage of persistent objects, that is, objects that
survive after the user session or application program that created them has terminated.
This is in contrast to transient objects that last only for the invocation of the program.
Persistent objects are retained until they are no longer required, at which point they are
deleted. Other than the embedded language approach discussed in Section 26.1.3, the
schemes we present next may be used to provide persistence in programming languages.
For a complete survey of persistence schemes, the interested reader is referred to Atkinson
and Buneman (1989).
Although intuitively we might consider persistence to be limited to the state of objects,
persistence can also be applied to (object) code and to the program execution state.
Including code in the persistent store potentially provides a more complete and elegant solution. However, without a fully integrated development environment, making code
persist leads to duplication, as the code will exist in the file system. Having program state
and thread state persist is also attractive but, unlike code for which there is a standard
definition of its format, program execution state is not easily generalized. In this section
we limit our discussion to object persistence.
A DBMS must provide support for the storage of persistent objects, that is, objects that
survive after the user session or application program that created them has terminated.
This is in contrast to transient objects that last only for the invocation of the program.
Persistent objects are retained until they are no longer required, at which point they are
deleted. Other than the embedded language approach discussed in Section 26.1.3, the
schemes we present next may be used to provide persistence in programming languages.
For a complete survey of persistence schemes, the interested reader is referred to Atkinson
and Buneman (1989).
Although intuitively we might consider persistence to be limited to the state of objects,
persistence can also be applied to (object) code and to the program execution state.
Including code in the persistent store potentially provides a more complete and elegant solution. However, without a fully integrated development environment, making code
persist leads to duplication, as the code will exist in the file system. Having program state
and thread state persist is also attractive but, unlike code for which there is a standard
definition of its format, program execution state is not easily generalized. In this section
we limit our discussion to object persistence.
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