Schema Mappings: From Data Translation to Data Cleaning

Schema mapping management is an important research area in data transformation, integration, and cleaning systems. The reasons for its success can be found in the declarative nature of its building block (thus enabling clean semantics and easy to use design tools) paired with the efficiency and modularity in the deployment step. In this chapter we cover the evolution of schema-mappings through what we identify as three main ages. We start presenting the foundations of schema mapping tools and the first tools aimed at translating data from a source to a target schema in the first, heroic age. We then discuss the silver age, when schema mapping tools have grown their way into complex systems and have been translated into both commercial and open-source tools. Finally, we show how recent results in schema-mapping are stimulating a third, golden age, with novel research opportunities and a new generation of systems capable of dealing with a significantly larger class of real-life applications.