An improved classification system for classifying characteristics of an
article into classes of characteristics based on features associated with
the characteristics. The system includes a first rule-based classifier
that provides rules that embody requirements of selected features so as to
together define selected classes. These rules are applied to measured
features of an article characteristic to assign one of the selected
classes to that characteristic, should the article characteristic meet the
feature requirements of one of the selected classes. The system also
includes a trainable classifier configured based on a training set of
preclassified characteristics, with the trainable classifier connected so
as to accept from the first rule-based classifier an article
characteristic not classified by the rule based classifier. The trainable
classifier assigns one of the training set classes to the unclassified
characteristic, should the trainable classifier configuration associate
that characteristic with one of the training set classes. A second
rule-based classifier can be connected so as to accept classified
characteristics from the trainable classifier for making refinement
classifications, and a third rule-based classifier can be connected so as
to accept unclassified characteristics from the trainable classifier for
making classification based on selected classes.