Mark doesn't influence Sweep, Sweep removes all?

[us...@domain.invalid]

I have created below RDF in memory:

<?xml version="1.0"?>
<RDF:RDF xmlns:NC="http://home.netscape.com/NC-rdf#"
xmlns:RDF="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
<RDF:Seq RDF:about="urn:root">
<RDF:li RDF:resource="urn:root:base_1"/>
<RDF:li RDF:resource="urn:root:base_2"/>
<RDF:li RDF:resource="urn:root:base_3"/>
</RDF:Seq>
<RDF:Description RDF:about="urn:root:base_2"
NC:id="2"
NC:name="10002" />
<RDF:Description RDF:about="urn:root:base_3"
NC:id="3"
NC:name="10003" />
<RDF:Description RDF:about="urn:root:base_1"
NC:id="1"
NC:name="10001" />
</RDF:RDF>

... and trying to Mark one and Sweep:

ds.QueryInterface(Components.interfaces.nsIRDFPurgeableDataSource);
ds.Mark(rdf.GetResource("urn:root:base_1"),
rdf.GetResource("http://home.netscape.com/NC-rdf#name"),
rdf.GetLiteral("1001"), true);
ds.Sweep();

... and it remove whole document. The result is:

<?xml version="1.0"?>
<RDF:RDF xmlns:NC="http://home.netscape.com/NC-rdf#"
xmlns:RDF="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
</RDF:RDF>

... what is wrong?

Alexander.

[us...@domain.invalid]