A flag to indicate the scope of the alignment between the
sequence of the entity or biological unit described in the data
block and that in the referenced database entry. 'entire'
indicates that alignment spans the entire length of both
sequences (although point differences may occur and can be
annotated using the data items in the STRUCT_REF_SEQ_DIF
category). 'partial' indicates a partial alignment. The region
(or regions) of the alignment may be delimited using data items
in the STRUCT_REF_SEQ category. This data item may also take
the value '.', indicating that the reference is not to a
sequence.