[BioSQL-l] parent_taxon_id of a root node

[Peter]

Hello all,

I was puzzled to find the BioSQL script load_ncbi_taxonomy.pl will set
the parent_taxon_id of the NCBI root node in the taxon table to point
to itself.  I would have expected this to be NULL indicating no
parent.  If someone is using the database directly, extracting a
lineage could trigger an infinite loop.  Can anyone explain the
rational here?

Note that when Biopython adds entries to the taxon table, it uses NULL
for a root node.  When retrieving sequences from a BioSQL database,
Biopython does cope with a root node with a NULL parent or a
self-parent - would it safe to assume BioPerl and Java can also cope
with both situations?

Thanks,

Peter