Create a logical Network Data Model in Oracle and it would be great to store RDF. That was what I thought after reading "Re: Chemistry and the Semantic Web".
The attached document is based on articles available from Oracle. An indepth description is available in "Network Data Model Overview" (free registration required).
There are various schemas defined for storing networks which includes:
"NODE_NAME VARCHAR2(32) Name of the node.
NODE_TYPE VARCHAR2(24) User-defined string to identify the node type."
The schema is obviously not designed to store RDF unlike other RDBMS mappings.
One difference is their flexibility in storing different graphs and giving links a "cost".
Another difference is their nodes and links are typed as strings; this looks like it would limit the effectiveness of data type operations. Querying for all nodes that are numbers between two values or dates between two ranges is going to be costly compared to dedicated data type handling. That's apart from the obvious difficulty in trying to put everything into a VARCHAR2(24).
Unless they have optimised the query layer specifically for the task, which might be case, it will also incur the costs of joining against the same table many 10s or 100s of times.
It does have some neat operations (like shortest-path), a Java API, PL/SQL integration and of course it integrates well with existing Oracle databases.