Read this article. Be sure you can explain the methods (approach) for extracting data based on usability.
3. The Conceptual Foundations of Data Reusability
In this section, we introduce a conceptual framework within which to address the data (re)usability problem from a more theoretical point of view. We have borrowed some concepts from other theoretical fields, i.e., relational thinking, levellism, and knowledge sharing in order to create this conceptual framework. We have identified these three fields because data (re)usability implies a relationship between the data author and data user; it requires that data must be made available at different levels of abstraction and representation, and it also requires that data be semantically enriched in order to be able to cross semantic barriers without semantic distortions.