Object-Oriented Programming Using SOM and DSOM/Making Your Objects Persistent

The Persistence SOM (PSOM) Framework allows you to make all or part of a SOM object persistent. This means you can p1·eserve the state of an object, ever after the process that creates the object terminates. The Framework provides services that allow you to store an object to a file system or another form of per sistent store. It also provides services that permit you restore objects from the persistent storage.

Most applications already use some form of persistence. For example, a spreadsheet or a word processor stores user data in a file. The implementation of a spreadsheet typically contains logic that converts the data in the cells into some format that can be written to a file for storage. When an existing spread sheet is loaded, the reverse takes place. The logic converts the external data back to the cell format so the user can work with it.

The PSOM Framework simplifies these operations by providing a uniform interface to storage. A cell in a spreadsheet can be implemented as a persistent object, and its data can be stored and restored, using the services in the PSOM Framework. Any flattening and unflattening of data can be eliminated. Applications can also avoid writing low level I/O routines and therefore become more portable.