The "Model" class is an optional Object to Document mapper for C++. You
would use it if you wanted to extend and existing class to have built-in
methods to save itself from MongoDB and to load itself from MongoDB.
When you implemented your inherited class, you'd write the 'serialize()'
and 'unserialize()' methods to use BSONObjBuilder to build a BSON
representation of this class.
Once you have an instance of the class, you can call the 'load()' method to
instantiate the class from the values stored in MongoDB, and call the
'save()' method to save the class values into MongoDB for later use.
Use of the "Model" class is definitely optional, and not recommended for
beginners. Unfortunately, I could not find any further documentation on
the use of this class, nor could I find any tutorial examples.
Let me know if you have further questions.