> The cost is you then can't make a single query across both at the same > time (without using SERVICE) but as the sources are independent, I can't > see how you can anyway. Instead ask one graph, get results, do whatever > mapping is needed, ask other graph.
OK this is what I don't understand. Using again HDT as a reference... I was able to create an assembler file, with one rdfdataset and multiple graphs, each graph pointing to a .hdt file. Then from SPARQL I could use "select from <graph-1> <graph-2> ..." and this worked. Basically what I'm trying to do is the same thing but using TDB(2) instead of HDT. I've setup the assembler, I can get a list of graphs from sparql, but then when I query one graph I get that "Error 500: Not in a transaction" error.
