For example:

I assume "hsa0071" is a pathway ID. So I want to extract all compound ID from that pathway using keggGet("hsa00071")[[1]]$COMPOUND.

I also notice there is keggGet("hsa00071")[[1]]$REL_PATHWAY object:

> keggGet("hsa00071")[[1]]$REL_PATHWAY
                                hsa00020                                     hsa00061 
             "Citrate cycle (TCA cycle)"                    "Fatty acid biosynthesis" 
                                hsa00062                                     hsa00072 
                 "Fatty acid elongation" "Synthesis and degradation of ketone bodies" 
                                hsa00561                                     hsa00630 
               "Glycerolipid metabolism"    "Glyoxylate and dicarboxylate metabolism" 
                                hsa00650 
                  "Butanoate metabolism"

I wonder what this REL_PATHWAY means? I want to make sure I extract in right way.

Thank you so much for your help.