Transforming XPath Expressions Into Relational Algebra Expressions with Kleene Closure

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Provided by: IARIA
Topic: Data Management
Format: PDF
In the problem of translating X-Path expressions into SQL queries, the most challenging part is to find a way to minimize the use of Least Fix-Point (LFP) operators when a DTD graph contains cycles. In this paper, the authors address this issue and present a new algorithm to do the task based on the recognition of a kind of DTD graphs, which can be reduced to a single node by contracting nodes into their parents one by one. For this kind of DTD graphs, not only the corresponding relational algebra expressions can be efficiently generated, but the use of LFP operators can also be minimized.
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