I have a question about PCC practice for the URLs for internet resources
that are no longer available.

LRI 9.7B says the following

2) If searching indicates that the resource is no longer available,
create a note to reflect this fact by changing subfield $u in field 856
to subfield $z and modifying the subfield to show that the resource is
no longer available, indicating the last date that the resource was
searched. ...

and gives the example
revised record
856 41 $z Electronic address (http://www.example.com) not available when
searched on [date]

However CONSER cataloging module module 31 (dated March 2012) says:

If the only link appearing on the CONSER record is an invalid link, it
can be left on the record and labeled as invalid in the subfield $z of
the 856 field. Note that the second indicator is blank and that the
non-working URL is maintained in subfield $u of the 856. This coding
differs from LC practice documented in LCRI 9.7B where the non-working
URL is moved to a subfield z so that it does not appear on LC’s link
checking reports repeatedly. The example below is based on a
recommendation from OCLC and is derived from current system indexing
needs and OCLC'€™s electronic address checking software (see OCLC'€™s
recommendation at:
http://www.oclc.org/support/documentation/worldcat/cataloging/electronicresources/).
856 4# $z Link no longer valid as of Dec. 4, 2000 $u http://www...

So, we're confused about which practice to follow, since it seems that
there are two conflicting PCC practices. This is also causing us
problems internally in our opac, since we can't suppress the display of
a hotlink if the URL is in $u. And we don't quite understand why one
would use a public rather than non-public note ($x) for this.


Thanks
Greta de Groat
Stanford University Libraries