Target Object (Liu, Web Data Mining book, 2006)
Definition (object): An object o is a product, person, event, organization, or topic. o is represented as
a hierarchy of components, sub-components, and so on.
Each node represents a component and is associated with a set of attributes of the component.
An opinion can be expressed on any node or attribute of the node.
To simplify our discussion, we use the term featuresto represent both components and attributes.