Schema mapping evolution

Schema Mapping Evolution Through Composition and Inversion...

While we cover more than 20 recent implementations and proposals, there are many more approaches that can be evaluated in a similar way than we do in this chapter. We refer the reader to the online bibliography on schema evolution under http // se-pubs.dbs.uni-leipzig.de (Rahm and Bernstein 2006) for additional related work. Book chapter 7 (Fagin et al. 2011) complements our paper by focusing on recent work on mapping composition and inversion that support the evolution of schema mappings. 

Commercial DBMS do not support abstract schema mappings but only SQL for specifying view mappings and evolution mappings. There is no support for multiple explicit schema and database versions. Once the DDL statements of an evolution step have been executed, the previous version of the evolved objects is gone. There is no support for applications that were developed against previous versions of the database. 

In this chapter, we show how two fundamental operators on schema mappings, namely composition and inversion, can be used to address the mapping adaptation problem in the context of schema evolution. We illustrate the applicability of the two operators in various concrete schema evolution scenarios, and we survey the most important developments on the semantics, algorithms, and implementation of composition and inversion. We also discuss the main research questions that still remain to be addressed. 

M, where the target schema of M is the source schema of M. The result is a schema mapping M o M that has the same effect as applying first M and then M. For our schema evolution context, M o M combines the original transformation M with the evolution mapping M . 

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