same containers in more datasources in one nsIRDFCompositeDataSource

Hi,

Imagine two datasources, that both has same resource, that is instance 
of rdf:Seq. When the two datasouces are added to some composite 
datasource, than the content of resource in the composite datasource is 
mixed together.

For example, container in first datasource:

   resource -> rdf:instanceOf -> rdf:Seq
            -> rdf:_1 -> Element 1
            -> rdf:_2 -> Element 2

The contaniner from second datasource:

   resource -> rdf:instanceOf -> rdf:Seq
            -> rdf:_1 -> Element 3
            -> rdf:_2 -> Element 4

The composite datasource does exactly what is expected - and the result 
is that if the composite datasource is used in some xml template, than 
the content of both resources is mixed together.

Is there any way how to "merge" contents of containers in composite 
datasource, with renumbering of the containers to produce something like

   resource -> rdf:instanceOf -> rdf:Seq
            -> rdf:_1 -> Element 1
            -> rdf:_2 -> Element 2
            -> rdf:_3 -> Element 3
            -> rdf:_4 -> Element 4

Thanks,
Jan