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Data exchange is the process of taking data structured under a ''source'' schema and actually transforming it into data structured under a ''target'' schema, so that the target data is an accurate representation of the source data.〔A. Doan, A. Halevy, and Z. Ives. "Principles of data integration", Morgan Kaufmann, 2012 pp. 276〕 Data exchange is similar to the related concept of data integration except that data is actually restructured (with possible loss of content) in data exchange. There may be no way to transform an instance given all of the constraints. Conversely, there may be numerous ways to transform the instance (possibly infinitely many), in which case a "best" choice of solutions has to be identified and justified. == Single-domain data exchange == Often there are a few dozen different source and target schema (proprietary data formats) in some specific domain. Often people develop a exchange format or interchange format for some single domain, and then write a few dozen different routines to (indirectly) translate each and every source schema to each and every target schema by using the interchange format as an intermediate step. That requires a lot less work than writing and debugging the hundreds of different routines that would be required to directly translate each and every source schema directly to each and every target schema. (For example, Standard Interchange Format for geospatial data, Data Interchange Format for spreadsheet data, GPS eXchange Format or Keyhole Markup Language for indicating GPS coordinates on the globe, Quicken Interchange Format for financial data, GDSII for integrated circuit layout, etc.) == Data exchange languages == A data exchange language is a language that is domain-independent and can be used for any kind of data. Its semantic expression capabilities and qualities are largely determined by comparison with the capabilities of natural languages. The term is also applied to any file format that can be read by more than one program, including proprietary formats such as Microsoft Office documents. However, a file format is not a real language as it lacks a grammar and vocabulary. Practice has shown that certain types of formal languages are better suited for this task than others, since their specification is driven by a formal process instead of a particular software implementation needs. For example, XML is a markup language that was designed to enable the creation of dialects (the definition of domain-specific sublanguages) and a popular choice now in particular on the internet. However, it does not contain domain specific dictionaries or fact types. Beneficial to a reliable data exchange is the availability of standard dictionaries-taxonomies and tools libraries such as parsers, schema validators and transformation tools. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Data exchange」の詳細全文を読む スポンサード リンク
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