In addition to standard FROM and FROM NAMED clauses, Virtuoso extends SPARQL with NOT FROM and NOT FROM NAMED clauses of "opposite" meaning.

SELECT ... NOT FROM <x> ... WHERE {...}

means "SELECT FROM other graphs, but not from the given one". This is especially useful because NOT FROM supports graph groups (NOT FROM NAMED supports only plain graphs). So if

<http://example.com/users/private>

is a graph group of all graphs with confidential data about users then

SELECT * NOT FROM <http://example.com/users/private> WHERE {...}

will be restricted only to insecure data.

NOT FROM overrides any FROM and NOT FROM NAMED overrides any FROM NAMED, the order of clauses in the query text is not important.

The SPARQL web service endpoint configuration string may contain pragmas input:default-graph-exclude and input:named-graph-exclude that become equivalent to NOT FROM and NOT FROM NAMED clauses like input:default-graph-uri and input:named-graph-uri mimics FROM and FROM NAMED.