DATE: Dec. 11, 1998


NAME: Field 263 and year 2000 compatibility in the MARC bibliographic format

SOURCE: Library of Congress; Academic Book Center

SUMMARY: This paper proposes a minor change to the structure of the date recorded in field 263 to make it Y2K conformant

KEYWORDS: Field 263 (Bibliographic); Projected publication date; Year 2000 compatibility


12/11/98 - Forwarded to the MARC Advisory Committee for discussion at the January 1999 MARBI meetings.

1/30/99 - Results of MARC Advisory Committee discussion - Approved.

4/15/99 - Results of LC/NLC review - Approved.

PROPOSAL NO. 99-07: Field 263 and year 2000 compatibility in the MARC bibliographic format


During the initial analysis of the year 2000 problem and the MARC formats, field 263 was identified as one of the data elements where the year is represented by two digits. At that time this was felt to be acceptable for projected publication dates and no changes were suggested for field 263. More recently that decision has come into question. This proposal takes a closer look at field 263 and the "Y2K" problem. It suggests changes to the structure of the information recorded in the field to make it completely Y2K compatible. Other problems related to ambiguities in encoding the data itself are also dealt with.


2.1. Use of field 263

Field 263 is used to record the projected publication date, usually in the form of a coded year and month, for works which have not yet been published. The encoding level (Leader/17) in records containing this field is generally set to value 8 (Prepublication level) to further identify the cataloging as "prepublication" and thus subject to change. The cataloging of bibliographic items by national bibliographic agencies such as the Library of Congress (LC) prior to their actual publication has proven to be a very useful in the U.S. and in other countries. The data in field 263 and Leader/17 value 8 can be used to perform periodic database maintenance of the cataloging for items which may not have been published yet, or which, for some reason, may never be published.

The Library of Congress, which produces "CIP" (Cataloging-in-Publication) records in the U.S., includes field 263 in all prepublication cataloging it does as part of its official CIP program. Periodic searches of its databases are done against field 263 to identify items which, based on the date in this field, should have been published and subsequently received by LC. Generally, LC claims any material once the date in field 263 has been passed and the item is still not received. The identification of records which fall into this category has been simple due to the structure of the year and month in field 263. Searches are done which limit the retrieved records to those which fall into specific date spans.

2.2. Current structure of field 263 data

The MARC content designation of field 263 is very simple. A single, non-repeatable subfield $a is used to record the structured date. The structure of the date recorded in subfield $a is equally simple. It consists of a two-digit year portion, followed by a two-digit month portion in the pattern yymm. The only special considerations made with the structured date is that single digit years and/or months are always right justified with unused positions containing zeros. When the publication is planned for a season rather than a particular month of the year, practice has been to use the last month of the season in the month portion of the structured date.

If either the year or month is unknown, the format prescribes the use of two hyphens (--) as place holders in the appropriate portion of the structured date. If the item has been published but LC has unable to obtain a copy, the format shows the LC local practice of using four hyphens ("----"), in field 263. The use of four hyphens is here is ambiguous with their use to represent unknown portions of the date.

2.3. Impact of the year 2000 problem

The arrival of the year 2000 will render ambiguous all structured dates which include two-digit-only year portions. This problem affects the year portion of field 263 as well. It was initially thought that there would be little problem with this ambiguity since the earliest CIP cataloging was not produced until the latter part of the 20th century and records with date prior to the current five years are generally weeded out of MARC databases as part of database maintenance. The initial analysis of the problem suggested that the current structure of field 263 dates could be lived with.

Recent reports from outside LC, the primary creator of MARC records including field 263, have indicated that other MARC record users occasionally do machine processing of field 263 data. The Academic Book Center, the most recent MARC user to report a problem, found that the Y2K incompatibility of field 263 made it impossible for computer programs to generate the century correctly, when they needed to do so. LC's own processing of data in field 263 would be equally foiled when trying to do logical retrieval limits based on the current two-digit year portion, unless special logic were built into the retrieval mechanism.

2.4. Impact of changes to the field 263 date structure

Although the Y2K incompatibility in field 263 is the least serious of all that have been found in the MARC formats, it has the advantage of being one of the easiest to fix. In LC's bibliographic databases, field 263 occurs in only 70,000 out of 4.6 million bibliographic records about 1.5 percent. OCLC has reported that the impact of changes to the structure of field 263 dates would be minimal. The only special processing done is a validation check on the length of subfield $a. A change to increase the length to six characters could be done easily. The same is true for other bibliographic utilities that do little more than load CIP cataloging records.

A change to the structure of the content of field 263 would be fairly easy to implement prospectively, but there are some considerations retrospectively for LC, who is the most active user of this field. LC is currently planning for the implementation of a new Integrated Library System in 1999. Part of the implementation planning involves the conversion of existing bibliographic records from an internal database structure to MARC for migration into the new system. At the time of conversion and loading, manipulation of legacy data is possible, but may not be done for field 263 data. For a period following the implementation of this new system, LC will need to continue to use a small number of older processing routines which are dependent on its existing field 263 structure. So it may never be feasible to restructure the 70,000 existing occurrences of field 263 in LC's files.. If any change to the field 263 data structure is approved, LC would be unable to implement this change until it processing routines, which are dependent on the old structure, can be changed. It is hoped that these old routine will be replaced as well by the end of 1999, but any exact date has not been set.

2.5. The Fix

The obvious fix of the Y2K incompatibility in field 263 would not require a change to the data elements defined in the MARC bibliographic format. It would simply require that the year portion of the field 263 date structure be expanded to four positions. Along with this change in the structure, it is recommended that another small change be made in the field 263 description. The local practice of using four hyphen to identify titles which are not received and not available can be deleted from the format since LC does not distribute records with this data and intends to signal this situation in the future in a locally defined data element that will not be distributed.


In the MARC Bibliographic format:

Go to:

Library of Congress
Library of Congress Help Desk (3/15/99)