Recursive XML Schemas, Recursive XML Queries, and Relational Storage: XML-to-SQL Query Translation. Krishnamurthy, R.; Chakaravarthy, V. T.; Kaushik, R.; and Naughton, J. F. In pages 42-53.
abstract   bibtex   
We consider the problem of translating XML queries into SQL when XML documents have been stored in an RDBMS using a schema-based relational decomposition. Surprisingly, there is no published XML-to-SQL query translation algorithm for this scenario that handles recursive XML schemas. We present a generic algorithm to translate path expression queries into SQL in the presence of recursion in the schema and queries. This algorithm handles a general class of XML-to-Relational mappings, which includes all techniques proposed in literature. Some of the salient features of this algorithm are: (i) It translates a path expression query into a single SQL query, irrespective of how complex the XML schema is, (ii) It uses the "with" clause in SQL99 to handle recursive queries even over non-recursive schemas, (iii) It reconstructs recursive XML subtrees with a single SQL query and (iv) It shows that the support for linear recursion in SQL99 is sufficient for handling path expression queries over arbitrarily complex recursive XML schema.
@inproceedings{ kri04,
  crossref = {icde2004},
  author = {Rajasekar Krishnamurthy and Venkatesan T. Chakaravarthy and Raghav Kaushik and Jeffrey F. Naughton},
  title = {Recursive XML Schemas, Recursive XML Queries, and Relational Storage: XML-to-SQL Query Translation},
  topic = {xsd[0.7]},
  pages = {42-53},
  uri = {http://csdl.computer.org/comp/proceedings/icde/2004/2065/00/20650042abs.htm},
  abstract = {We consider the problem of translating XML queries into SQL when XML documents have been stored in an RDBMS using a schema-based relational decomposition. Surprisingly, there is no published XML-to-SQL query translation algorithm for this scenario that handles recursive XML schemas. We present a generic algorithm to translate path expression queries into SQL in the presence of recursion in the schema and queries. This algorithm handles a general class of XML-to-Relational mappings, which includes all techniques proposed in literature. Some of the salient features of this algorithm are: (i) It translates a path expression query into a single SQL query, irrespective of how complex the XML schema is, (ii) It uses the "with" clause in SQL99 to handle recursive queries even over non-recursive schemas, (iii) It reconstructs recursive XML subtrees with a single SQL query and (iv) It shows that the support for linear recursion in SQL99 is sufficient for handling path expression queries over arbitrarily complex recursive XML schema.}
}
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