Relational and XML Data Exchange
Data exchange is the problem of finding an instance of a target schema, given an instance of a source schema and a specification of the relationship between the source and the target. Such a target instance should correctly represent information fromthe source instance under the constraints impos...
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| Những tác giả chính: | , , , |
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| Định dạng: | Sách |
| Ngôn ngữ: | English |
| Được phát hành: |
Morgan and Claypool Publishers
2011
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| Những chủ đề: | |
| Truy cập trực tuyến: | https://scholar.dlu.edu.vn/thuvienso/handle/DLU123456789/26142 |
| Các nhãn: |
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| Thư viện lưu trữ: | Thư viện Trường Đại học Đà Lạt |
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| Tóm tắt: | Data exchange is the problem of finding an instance of a target schema, given an instance of a
source schema and a specification of the relationship between the source and the target. Such a
target instance should correctly represent information fromthe source instance under the constraints
imposed by the target schema, and it should allow one to evaluate queries on the target instance
in a way that is semantically consistent with the source data. Data exchange is an old problem that
re-emerged as an active research topic recently, due to the increased need for exchange of data in
various formats, often in e-business applications.
In this lecture, we give an overview of the basic concepts of data exchange in both relational
and XML contexts.We give examples of data exchange problems, and we introduce the main tasks
that need to addressed.We then discuss relational data exchange, concentrating on issues such as
relational schema mappings, materializing target instances (including canonical solutions and cores),
query answering, and query rewriting. After that, we discuss metadata management, i.e., handling
schema mappings themselves.We pay particular attention to operations on schema mappings, such
as composition and inverse. Finally, we describe both data exchange and metadata management in
the context of XML.We use mappings based on transforming tree patterns, and we show that they
lead to a host of new problems that did not arise in the relational case, but they need to be addressed
for XML. These include consistency issues for mappings and schemas, as well as imposing tighter
restrictions on mappings and queries to achieve tractable query answering in data exchange. |
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