Hi Hilmar,
See beyound a short explanation about what is a Persistent Object Framework (POF).
I think that XMLAdapter() could be a way to resolve part of this framework.

Persistent Object Framework :
In programming languages such as VFP, you create and manipulate
objects. These objects reside in memory while the program is running.
When the program ends, the objects cease to exist, and memory is freed
for use by the operating system. These objects are transient objects.
In contrast, persistent objects continue to exist after the program ends.
For this persistence to occur, the objects must be stored in persistent
storage, such as a file or database. Because databases address issues
such as concurrent access by multiple users, security, and backup
facilities, a database is the obvious choice for persistent storage.

Making objects persistent:
As previously described, an object consists of attributes (data), and
methods (behavior). For an object to become persistent, its attributes and
methods must be stored. An object’s methods are stored in the program
as part of a class. You can store the object’s data (state or attributes) in a
database.
When you retrieve the object from persistent storage, you can update
some of the object’s state, or delete the object when it is no longer
needed. The POF provides the facilities to store, retrieve, update, and
delete the object data in a database.

Persistent storage:
Before creating a persistent object, you must know how to make objects
persistent and the ways you can store the objects.
Objects are persistent when they are stored. There are two basic types of
persistent stores that can maintain objects:
♦ Files. Store the object, but they are limiting in size and accessibility.
♦ Databases. Provide concurrency management, multiple-user
accessibility, and mission-critical features found in most databases.
The primary types of databases used to store objects are object and
relational databases.

Persistent frameworks:
A framework is a set of classes that work together to perform designated
functions. A persistency framework is a set of classes that work together
to make application objects persistent, allowing you to store, retrieve,
update, and delete user-defined objects. The framework should support
database access-related services, such as concurrency and transaction
management, and should complement the functionality of the persistent
store to provide full persistent services.

The primary benefits of using a persistent framework are:
♦ Database access is encapsulated. Database access is shielded
from the application, which makes it easier to change the underlying
database.
♦ Database access is simplified. You can more easily implement
database access features in your applications.
♦ Framework is extensible. You can incorporate your own classes
and features into the framework.