Data can be defined as simple facts, divorced from information about what to do with them. “Data” has a dusty whiff about it, the old-fashioned ring of data processing or data structures.
Data is often a natural starting point for thinking about things. For example, we know we have a first name, middle name, and last name, so we create a Person class with that information. But objects are about data and behavior together—your code will be more robust if you organize objects by behavior.
Data-oriented objects are an opportunity. The smells in this chapter are often signs of a missing or inadequately formed class. If the data represents a good clustering, we'll usually be able to find behavior that belongs in the class.