We have been trying to build a taxonomic backbone for the India Biodiversity Portal and it is a challenging task.
The obkective is to hve a taxonomic backbone so that all biodiversity content can be referenced in the tree of life. The backbone should be flexible because taxonomic revisions are being made continuously. Also except for birds and mammals, in the Indian context, the taxomomy of many groups are still evolving and new species are being deiscoverd and reported.
GBIF also faces similar challenges and they are trying to build a new system. Look at the blog here