http://purl.uniprot.org/uniprot/P00750 is a permanent URL for a
uniprot database entry. A database entry is an information resource,
hence http://purl.uniprot.org/uniprot/P00750 should not return 303,
but instead the database record. Assuming for a moment you're using a
browser that would be the HTML representation.
Non-information should use a 303 indirect. But a 303-indirect does not
imply the source URI identifies a non-IR.
A 303 means: The representation of this resource can not be given. But
here are some additional information, please go there and see. The
reason that the representation cannot be given are many. Being non-IR
is just one of them.
Xiaoshu
