While working on issue #7959, I noticed that many schema node objects do not have a common schema-specific node base class.  For example, all of table node classes are derived from ATableNode, but not view node classes and column node classes. Lacking a schema-specific node base class results many duplicated codes, it also makes other objects (such as action objects) harder to implement.

When we have time, we might want to do a design review and decide whether we want to create a schema-specific node base class for each of supported schema node type.