@inbook {COV06 ,
	title = {Type-safe two-level data transformation },
	booktitle = {FM 2006: Formal Methods},
	series = {LNCS},
	volume = {4085},
	year = {2006},
	month = {Aug.},
	pages = {284-299},
	publisher = {Springer-Verlag},
	organization = {Springer-Verlag},
	address = {Hamilton, Ontario, Canada},
	abstract = {<p>A two-level data transformation consists of a type-level transformation of a data format coupled with value-level transformations of data instances corresponding to that format. Examples of two-level data transformations include XML schema evolution coupled with document migration, and data mappings used for interoperability and persistence.<br />
We provide a formal treatment of two-level data transformations that is type-safe in the sense that the well-formedness of the value-level transformations with respect to the type-level transformation is guarded by a strong type system. We rely on various techniques for generic functional programming to implement the formalization in Haskell.<br />
The formalization addresses various two-level transformation scenarios, covering fully automated as well as user-driven transformations, and allowing transformations that are information-preserving or not. In each case, two-level transformations are disciplined by one-step transformation rules and type-level transformations induce value-level transformations. We demonstrate an example hierarchical-relational mapping and subsequent migration of relational data induced by hierarchical format evolution.</p>
},
	doi = {10.1007/11813040_20},
	url = {http://link.springer.com/chapter/10.1007\%2F11813040_20},
	author = {Alcino Cunha and Jos{\'e} Nuno Oliveira and Joost Visser}
}