nsIRDFDataSource* ds = NS_STATIC_CAST(nsIRDFDataSource*, mDataSources[i]); nsresult rv = ds->DoCommand(aSources, aCommand, aArguments);
nsresult rv = mDataSources[i]->DoCommand(aSources, aCommand, aArguments);
CompositeDataSourceImpl::DoCommand(nsISupportsArray/*<nsIRDFResource>*/* aSources,                                   nsIRDFResource*   aCommand,                                   nsISupportsArray/*<nsIRDFResource>*/* aArguments){    for (PRInt32 i = mDataSources.Count() - 1; i >= 0; --i) {        nsIRDFDataSource* ds = NS_STATIC_CAST(nsIRDFDataSource*, mDataSources[i]);        nsresult rv = ds->DoCommand(aSources, aCommand, aArguments);        if (NS_FAILED(rv) && (rv != NS_ERROR_NOT_IMPLEMENTED))        {		return(rv);   // all datasources must succeed	}    }    return(NS_OK);}