However, in the meta class, the methods use resampling and voting for classification and regression, and the methods in the other classes are considered model units, such as AdaBoost  and Bagging .
The meta class and trees class methods performed better than those in other classes for the two types of BRCA genomics data (mRNA in Figure 2 and miRNA in Figure 4), as evidenced by the best medians and averages.
The misc class was best in the OV-mRNA group datasets, but the meta class had relatively better prediction performance for the OV-miRNA group.
No methods in the meta class were eliminated, which indicated that methods based on resampling and an ensemble mechanism were stable and could address varied datasets even they were not always the best.
The various distributions in Figures 2, 4, 6, 8, 10, and 12 indicate that the methods in the meta class are relatively stable for prediction, which is reasonable because the methods in the meta class use other methods for ensemble learning, so they are not sensitive to different dataset distributions as other types of methods are.
The trees class was slightly benefited in the BRCA-miRNA group but was not globally affected as the meta class was.
Class environments are built when the HBMS server begins execution and when new classes are loaded into the HBMS server with the set-class method of Meta Class (see section Class Evolution).
Meta Class provides basic operations on the class inheritance hierarchy: get-class, set-class, delete-class, and create instance.
A new (version of a) class is created by sending the set-class message to Meta Class containing a class description consisting of two parts: a list of default attributes and specifications of methods operating on the attributes.
Initially, the five subclasses of Object were developed from scratch using the object-oriented kernel (Meta Class and Object class) [Will and Leggett 1992].
All expressions evaluating to anything other than false cause an event to be generated and transmitted to the subscribing user, send-events can be included in all methods in subclasses created in the HBMS server and is (by default) invoked when using the methods of Meta Class and System Object, since these cannot be versioned or subclassed, send-events can also be invoked with specific parameters allowing "high-level" events to be generated (for instance, events describing actions performed in the tool integrator instead of the HBMS server).
In fact, the data-modeling component in the TI is a modified version of the object-oriented kernel (Meta Class and Object class) in the HBMS server.