With the emergence of the Web and the wide use of XML for representing data,
the ability to map not only flat relational but also nested data has become
crucial. The design of schema mappings is a semi-automatic process. A human
designer is needed to guide the process, choose among mapping candidates, and
successively refine the mapping. The designer needs a way to figure out
whether the mapping is what was intended. Our approach to mapping validation
allows the designer to check whether the mapping satisfies certain desirable
properties. In this paper, we focus on the validation of mappings between
nested relational schemas, in which the mapping assertions are either
inclusions or equalities of nested queries. We focus on the nested relational
setting since most XML?s Document Type Definitions (DTDs) can be represented
in this model. We perform the validation by reasoning on the schemas and
mapping definition. We take into account the integrity constraints defined on
both the source and target schema. We consider constraints and mapping?s
queries which may contain arithmetic comparisons and negations. This class of
mapping scenarios is significantly more expressive than the ones addressed by
previous work on nested relational mapping validation. We encode the given
mapping scenario into a single flat database schema, so we can take advantage
of our previous work on validating flat relational mappings, and reformulate
each desirable property check as a query satisfiability problem.
Metalearning to choose the level of analysis in nested data: A case study on error detection in foreign trade statistics
