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Programming languages that natively and seamlessly allow objects to continue existing after the program has been closed down are called persistent programming languages. JADE is one such language.
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A persistent programming language is a programming language extended with constructs to handle persistent data. It is distinguished from embedded SQL in at least two ways:
In a persistent programming language:
- The query language is fully integrated with the host language and both share the same type system.
- Any format changes required between the host language and the database are carried out transparently.
In Embedded SQL:
- Where the host language and data manipulation language have different type systems, code conversion operates outside of the OO type system, and hence has a higher chance of having undetected errors.
- Format conversion must be handled explicitly and takes a substantial amount of code.
Using Embedded SQL, a programmer is responsible for writing explicit code to fetch data into memory or store data back to the database. In a persistent programming language, a programmer can manipulate persistent data without having to write such code explicitly.
The drawbacks of persistent programming languages include:
- While they are powerful, it is easy to make programming errors that damage the database.
- It is harder to do automatic high-level optimization.
- They do not support declarative querying well.
