We all structure information in our brains: without structure, we would not be able to deal with the huge quantities of highly heterogenous information we process. However, each of us structures this information slightly differently, often leading to misunderstandings or requiring additional rounds of dialog to clarify. Database schema are also designed by humans. The structure imposed on the information by the schema reflects the human designers' perspective on the world, even if mediated through formal design techniques or computer software. Therefore, the structured data querying task can be viewed as having a schema mapping problem at its core: mapping between the "schema" the human has in her brain and the schema used to organize the database.