Multiple TDB's in one assembly?

[Benson Margulies]

Using the sparql command (and some trickery to get tdb into the classpath):

@prefix tdb:     <http://jena.hpl.hp.com/2008/tdb#> .
@prefix rdfs:    <http://www.w3.org/2000/01/rdf-schema#> .
@prefix rdf:     <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix ja:      <http://jena.hpl.hp.com/2005/11/Assembler#> .

[] ja:loadClass "com.hp.hpl.jena.tdb.TDB" .
tdb:DatasetTDB  rdfs:subClassOf  ja:RDFDataset .
tdb:GraphTDB    rdfs:subClassOf  ja:Model      .

<#dataset> rdf:type         tdb:DatasetTDB ;
    tdb:location "/users/benson/data/1k_news.tdb" ;
    .

<#dataset2> rdf:type         tdb:DatasetTDB ;
    tdb:location "/users/benson/data/1k_news.cleaned.tdb" ;
    .



com.hp.hpl.jena.sparql.ARQException: More than one: var ?root
        at 
com.hp.hpl.jena.sparql.util.QueryExecUtils.getOne(QueryExecUtils.java:329)
        at 
com.hp.hpl.jena.sparql.util.graph.GraphUtils.findRootByType(GraphUtils.java:179)
        at 
com.hp.hpl.jena.sparql.core.assembler.AssemblerUtils.build(AssemblerUtils.java:80)
        at arq.cmdline.ModAssembler.create(ModAssembler.java:55)
        at 
arq.cmdline.ModDatasetAssembler.createDataset(ModDatasetAssembler.java:31)
        at 
arq.cmdline.ModDatasetGeneralAssembler.createDataset(ModDatasetGeneralAssembler.java:21)
        at arq.cmdline.ModDataset.getDataset(ModDataset.java:22)
        at arq.query.getDataset(query.java:100)
        at arq.query.queryExec(query.java:114)
        at arq.query.exec(query.java:91)
        at arq.cmdline.CmdMain.mainMethod(CmdMain.java:85)
        at arq.cmdline.CmdMain.mainRun(CmdMain.java:47)
        at arq.cmdline.CmdMain.mainRun(CmdMain.java:34)
        at arq.query.main(query.java:49)
        at arq.sparql.main(sparql.java:15)