Re: talk Digest, Vol 72, Issue 12Jim Melton jim.melton at acm.org
Thu Apr 30 11:46:49 PDT 2009
On Tue, Apr 28, 2009 at 9:34 PM, McBeath, Darin W (ELS-STL) <http://x-query.com/mailman/listinfo/talk> wrote: > > I'm curious if anyone has investigated or developed a transformation which > > takes a query expressed in SPARQL syntax to one roughly expressed in an > > equivalent XQuery syntax. I realize that there will likely not always be a > > direct 1 to 1 mapping, will be dependencies on the underlying XML document > > structure, and that some of the queries could become quite complex. I have not actually done the work to transform SPARQL into XQuery, but I have done considerable work (with considerable help!) on transforming SPARQL into SQL and have demonstrated (if not actually *proved*) that SPARQL and SQL are isomorphic. By that, I mean that, given a suitable SQL tabular representation of RDF (such as, but necessarily, a single table of three columns), it is possible to rewrite a SPARQL query into an SQL query on that representation of the RDF that produces the same result that the SPARQL query would have produced when run on a "native" RDF store. My company has also done very considerable work on transforming XQuery into SQL and have (for all practical purposes, although not mathematically) proven that XQuery and SQL are also isomorphic, given some suitable tabular representation of XML data. I assert with some confidence that if XQuery and SQL are isomorphic, and SQL and SPARQL are isomorphic, then XQuery and SPARQL are also isomorphic. I should point out that the SQL generated by the transformation process I and my colleagues devised was exceedingly ugly, complex, and visually inefficient; however, any reasonably competent SQL optimizer would be able to optimize away most, if not all, of the inefficiencies, provided the table(s) was(were) provided with suitable indexes. I would expect something similar from any transformation from SPARQL to XQuery. Hope this helps, Jim ======================================================================== Jim Melton --- Editor of ISO/IEC 9075-* (SQL) Phone: +1.801.942.0144 Chair, W3C XML Query WG; XQX (etc.) editor Fax : +1.801.942.3345 Oracle Corporation Oracle Email: jim dot melton at oracle dot com 1930 Viscounti Drive Standards email: jim dot melton at acm dot org Sandy, UT 84093-1063 USA Personal email: jim at melton dot name ======================================================================== = Facts are facts. But any opinions expressed are the opinions = = only of myself and may or may not reflect the opinions of anybody = = else with whom I may or may not have discussed the issues at hand. = ========================================================================
PURCHASE STYLUS STUDIO ONLINE TODAY!
Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!
Download The World's Best XML IDE!
Accelerate XML development with our award-winning XML IDE - Download a free trial today!
Subscribe in XML format