Accessor method for the general witness description.
+=head2 has_source
+
+Boolean method that returns a true value if the witness was created with a
+data source (that is, a file, string, or object to be parsed).
+
=head2 is_layered
Boolean method to note whether the witness has layers (e.g. pre-correction
=over
+=item * Figure out how to serialize a witness
+
=item * Support encodings other than UTF-8
=back