DATE: May 14, 1999

NAME: Defining URL/URN Subfields in the MARC 21 Bibliographic Format

SOURCE: Library of Congress CONSER Program; ALCTS Preservation and Reproduction Section, Intellectual Access Committee; Society of American Archivists' Technical Subcommittee on Descriptive Standards

SUMMARY: This proposal suggests the definition of subfields to contain URLs and URNs in bibliographic format fields other than field 856. Fields included are: 555, 583, 76X-78X.

KEYWORDS: Uniform Resource Locator; URI; Uniform Resource Name; URN; Field 555 (BD); Field 583 (BD, HD); Field 760-787 (BD); Cumulative Index/Finding Aids Note (BD); Action Note (BD, HD); Linking Fields (BD)

RELATED: DP 112 (Jan. 1999)


5/14/99 - Forwarded to the MARC Advisory Committee for discussion at the June 1999 MARBI meetings.

6/26/99 - Results of MARC Advisory Committee discussion: Approved in part.
Option 2 (define subfield $u as Uniform Resource Identifier, to contain a URL or URN) was approved for fields 555 and 583. The definition of a URI subfield in the linking entry fields was deferred. The general consensus was that the 76X-78X fields should be further studied as it was not clear what it would link to. Field 773 for aggregators seemed the most appropriate at this time. Several other fields were suggested as candidates for defining a URI subfield. Further proposals may be considered in the future. The new subfield $u in fields 555 and 583 will be repeatable because only one subfield is defined for URL or URN and it may be necessary to have both in the field. The documentation will stipulate that it should only be repeated if both are being recorded and not for additional URLs. It was suggested that the definition of separate subfields in field 856 for URL and URN ($g for URN and $u for URL) be reconsidered.

7/21/99 - Results of LC/NLC review - Approved.

PROPOSAL NO. 99-08: Defining URL/URN Subfields in the MARC 21 Bibliographic Format


Since the definition of field 856 (Electronic Location and Access) and its increasing use to link to electronic resources, needs have been expressed to define an electronic link in several other fields of the MARC 21 bibliographic format. Because of the potential to have repeatable 856 fields in the record (e.g. for varying locations of the same resource, for different versions, for different access methods, for subsets), it might be clearer to use specific fields already defined for the desired link. In addition, redundant keying is necessary to both provide the information in a note and then to provide the link in field 856. Although it is possible to include a URL in a note and have it activated as a hypertext link regardless of the fact that it is not specifically subfielded as such, it is preferable to define a specific subfield for various reasons, such as indexing, the ability to apply link updating software, etc.

Discussion Paper No. 112 (Defining URL/URN subfields in fields other than field 856 in the MARC Bibliographic/Holdings Formats) was discussed at the Midwinter meetings of the MARC Advisory Committee. The paper discussed the possibility of defining subfields to record URLs and/or URNs in various fields in the bibliographic format. These included field 037 (Source of Acquisition) for online ordering and field 583 (Action Note) for the location of supplemental information concerning preservation actions. The discussion revealed a general interest in pursuing the definition of these subfields for specified fields. Other applicable fields were mentioned as candidates, although the consensus was not to define these in any fields in which they might be applicable unless specific needs were determined.


The definition of a URL subfield in other fields has been discussed before, when its definition was considered in a subfield of the linking entry fields (in Discussion Paper No. 87 in June 1995). The recent discussion of D.P. 112 has indicated that the volatility of the URL should be a consideration for the cataloger, but should not prevent it from being defined elsewhere in the format. However, some guidelines are needed for indicating when it should be included in field 856 and when in the more specific field . A suggested guideline is the following: if the URL is a link to the resource itself that is described in field 245 of the record , then field 856 should be used. If it is to a related resource that is covered by another field (e.g. a link to a finding aid, a link to an action note), it is used in the specific field.

2.1. Fields requested

Various groups have requested the definition of a URL and/or URN to provide an electronic link to another resource. Other fields are obvious candidates for an electronic link and may have come up in previous discussion. This proposal includes only those fields for which a specific request has been made with sufficient justification. Others may be considered in the future, but in each consideration needs to be given to the implications of using a link in each field for which it is requested. Some other fields that have been mentioned, but that have not been given adequate justification or no group has specifically requested them are: field 505 (Formatted Contents Note); field 510 (Citation/References Note); Field 520 (Summary, Etc.); Field 530 (Additional Physical Form Available); Field 535 (Location of Originals/Duplicates); Field 544 (Location of Other Archival Materials); Field 545 (Biographical or Historical Data).

The previous discussion paper included the possibility of defining a URI subfield in field 037 (Source of Acquisition) for an electronic address. This would be useful for Web-accessible order information for documents, particularly for the Government Printing Office, which distributes some of its documents only through the Web and would contain a URI for an order form. However, since GPO has indicated that it probably would not include the information in records because of the difficulty in maintaining it, this proposal does not include adding a subfield in field 037. If others find it useful, it could be specifically requested.

Note that the term "URI" (Uniform Resource Identifier) is used to include both URLs and URNs.

2.2. Field 555 (Cumulative Index/Finding Aids Note)

A link to an electronic finding aid in field 555 has been specifically requested by the Society of American Archivists' Technical Subcommittee on Descriptive Standards. The link to an online copy of a more detailed surrogate description for a collection (finding aid) would be useful in the field, since it would eliminate the current redundancy now practiced by recording the finding aid in the note field as well as the 856. Currently separating the reference to the finding aid based on its form (if electronic, use 856; if not use 555) results in having to look in two different fields for the same sort of information. Field 856 would continue to be used to point to digital versions of the collection itself (i.e. that which is described in field 245).

The following subfield in field 555 are defined:

    $a - Cumulative index/finding aids note (NR) 
    $b - Availability source (R) 
    $c - Degree of control (NR) 
    $d - Bibliographic reference (NR) 
    $3 - Materials specified (NR)

100 1# $aJackson, Shirley $d1919-1965
245 00 $aPapers of Shirley Jackson, $f1932-1970 $g(bulk 1932-1965)
555 8# $aFinding aid available in the Manuscript Reading Room and on Internet. $u

If a URN were also recorded, it could either use a repeatable subfield $u or a separate URN subfield (here, uses $q):
555 8# $aFinding aid available in the Manuscript Reading Room and on Internet. $qurn:hdl:loc.mss/eadmss.ms996001 $u

2.3. Field 583 (Action Note)

The ALCTS Preservation and Reproduction Section, Intellectual Access Committee, has requested that subfield $u be defined in field 583 (Action Note) to record the location of external or supplemental information maintained on the Internet or in local automated files.

The following subfields in field 583 are defined:

     $a - Action (NR) 
     $b - Action identification (R) 
     $c - Time of action (R) 
     $d - Action interval (R) 
     $e - Contingency for action (R) 
     $f - Authorization (R) 
     $h - Jurisdiction (R) 
     $i - Method of action (R) 
     $j - Site of action (R) 
     $k - Action agent (R) 
     $l - Status (R) 
     $n - Extent (R) 
     $o - Type of unit (R) 
     $x - Nonpublic note (R) 
     $z - Public note (R) 
     $3 - Materials specified (NR) 
     $5 - Institution to which field applies (NR) 

583 27 $a deacidify $c 19860501 $u
An item that has been deacidified and for which treatment informaton is available through the World Wide Web at the specified URL.

583 27 $a house $c 19841221 $u
An item that has been housed and for which housing informaton is available through the World Wide Web at the specified URN.

2.4. Fields 76X-78X (Linking Entry fields)

Discussion Paper No. 87 (Addition of Subfield $l (Uniform Resource Locator) in Linking Entry Fields 76X-78X in the USMARC Bibligraphic Format) was presented at the MARC Advisory Committee meetings in June 1995. The paper suggested that a subfield for a URL be defined in the linking entry fields so that a machine link could be provided to a related electronic resource. This would enable the user to link to the related resource without having to go to the record for that resource itself. After discussion it was not requested that the issue come back as a proposal primarily because of the volatility of URLs. However, it needs to be reconsidered whether a subfield for an electronic link should be defined.

Because of the potential of having many 856 fields in the record for varying purposes, an indicator was defined in the field with Proposal No. 97-01 to indicate the relationship of the data in the field to the resource described in the record. The indicator values distinguish between an 856 that describes the resource itself, an electronic version of the resource described, and a related resource. This was needed because of the inability to provide the information in the specific linking entry field.

The Task Group on Journals in Aggregator Databases was established to investigate and make recommendations for a useful, cost-effective, and timely means for providing records to identify full-text electronic journals acquired in aggregator databases. These databases are being provided from various sources to bring together the full text of electronic journals. The group is exploring the creation of records for the electronic journals by the vendor which puts up the aggregator database. Note that it is not clear whether a separate record would be created for the electronic resource or whether the single record approach would be used in which the electronic journal is referenced on the record for the print (in cases where it is a clear reproduction of the original).

Currently the only method in the format that could be used to provide a link to the aggregator database from the record for the electronic journal is to use subfield $3 in field 856 to indicate that it is an aggregator database and to record the URI in that field. Further information about the aggregator would be in the linking entry fields (in field 773 (Host Item Entry)). However, it would be necessary to define a link code to be used with subfield $8 (Field link and sequence number) to allow for the field to link to the appropriate 773 field, since there may be multiple aggregator databases included in repeated 773 fields in the record. It would be more efficient and less cumbersome to record all the information in one field.

Defining a subfield for a URI in the linking entry fields would also be useful for other fields in the block. For instance, an electronic journal which changes its title could include a link to the succeeding entry (also an electronic journal) in field 785. However, guidelines may be necessary to determine when to use field 856 with second indicator value 2 (Related resource) and when to use the URL or URI subfield in the linking entry field.

The only subfields available in the 76X-78X block are subfields $l and $q. If separate subfields were defined for URL and URN, then both would have to be used. Alternatively, a single repeatable $l could be used.

The following subfields in fields 76X-78X are defined:

        $3 - Materials specified (NR) [773 only]
        $7 - Control subfield (NR)
        $a - Main entry heading (NR)
        $b - Edition (NR)
        $c - Qualifying information (NR) [except 773]
        $d - Place, publisher, and date of publication (NR)
        $e - Language code (NR) [775 only]
        $f - Country code (NR) [775 only]
        $g - Relationship information (R)
        $h - Physical description (NR)
        $i - Display text (NR)
        $j - Period of content (R) [786 only]
        $k - Series (R)  [all except 760 and 762]
        $m - Material-specific details (NR)
        $n - Note (R)
        $o - Other item identifier (R)
        $p - Abbreviated title (NR)  [773 and 786 only]
        $r - Report number (R) [all except 760, 762, and 777]
        $s - Uniform title (NR)
        $t - Title (NR)
        $u - Standard Technical Report Number (NR) [all except 760, 762, and 777]
        $v - Source contribution (NR) [786 only]
        $w - Record control number (R)
        $x - International Standard Serial Number (NR)
        $y - CODEN Designation (NR)
        $z - International Standard Book Number (R)  [all except 760, 762, and 777]

245 00 $a Psychology today $h [computer file]
260 ## $a [New York, NY, etc. : $b Sussex Publishers, etc.]
773 0# $t Academic search elite $d Ipswich, MA : EBSCO Publishing, 1999- $x 1071-2720 $l
[Includes a link to EBSCO Host, an aggregator database.]

2.5. Recording URNs

Proposal No. 97-9 (Renaming of Subfield 856$u to Accommodate URNs) was approved in June 1997. Instead of renaming subfield $u as URI to accommodate both URLs and URNs, it defined a different subfield for the URN. Consequently, subfield $g was defined as URN, to include all kinds of Uniform Resource Names (e.g. DOIs, handles). The subfield has not been used widely yet, but it is likely that in the future URNs will become more prevalent on the Web as persistent names for electronic resources.

All the above fields except 76X-78X have subfield $u available, which could be defined for the URL. Subfield $l could be defined in 76X-78X. There are two options to consider for the URN.

2.5.1. Option 1: Define a separate subfield for the URN. As with field 856, a separate subfield could be used for a URN. Since there are only two subfields available in fields 76X-78X (subfields $l and $q) and it is desirable to use the same across the fields, one of these could be defined as the URN. (It is not possible to define $u across all fields, since it is not available in 76X-78X. It seems preferable to define $u in all fields except the latter, since it is used in 856, rather than use $l everywhere except 856. In terms of repeatability, the subfields could agree with those in field 856, in which $u is non-repeatable and $g is repeatable. In this case, if more than one URL were applicable, the field would be repeated. (It might be considered whether subfield $g should have the same repeatability as $u in field 856.)

2.5.2. Option 2: Define a single subfield for Uniform Resource Identifier (URI) to contain either a URL or URN. Instead of defining another subfield in these fields, URNs could be distinguished by the initial "urn:", which is already a part of the string used. The subfield would have to be repeatable in case both a URL and a URN needed to be recorded. Since subfield $u in field 856 was made non- repeatable with Proposal No. 99-06 (Repeatability of subfield $u (URL) in field 856 of the MARC formats), if this option were approved, the format would need to state that the subfield could only be repeated if recording both a URL and a URN.

Example of a URN:
Title in 245: Map of New York City, Brooklyn, and vicinity, shewing [sic] suburban lines of Long Island Railroad and its connections.


In the MARC 21 Bibliographic Format:

Option 1:

Option 2:

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