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> and the arising problems? the most difference betwwen RDF
> and pure XML is the data model which is hierarchical tree for XML
> and graph for RDF.so if storing RDF in NXD,maybe it is
> needed to redesign the storage model and also mapping rdf query
> like RQL into XML query language like XQuery.
> It seems that the most appealing thing to store RDF in NXD
> is that i can utilize the index and other optimizing
You are correct; the difference in data model makes it difficult to get
any advantage from Xquery. The same applies to indexing though. The
idices which are supported by native XML databases are not RDF-aware.
However, we could make the same criticism of relational databases -- the
RDF data model is not at all like the relational data model; so vendors
have been forced to implement custom indexing and query schemes atop
relational engines. Since it requires a lot of custom work either way,
I do not think that either relational or native-XML have a distinct
advantage over the other, except for the fact that relational engines
are more mature, and targeting relational makes it easier to port a RDF
engine to multiple platforms. A native XML database would perhaps have
an easier time preserving the full fidelity of the input RDF documents,
but it is also possible for a relational-backed engine to store the
source RDF in a CLOB when shredding the RDF to relational tables.