Linked data and URIs #2-- Where are They?

Nowadays, URIs are found in numerous MARC fields. Consult a version of MARC documentation (Ex. https://www.oclc.org/bibformats/en/home.html or https://www.loc.gov/marc/bibliographic/ ) to verify that a particular MARC field contains a subfield for URIs.

URIs may sometimes be added to MARC fields without subfield coding (for example, in parentheses or after a dash to indicate a source of data in a note field). However, when URIs are separately coded, they are used in only a few subfields (For a fuller explanation, see https://www.oclc.org/bibformats/en/controlsubfields.html):

$u Uniform Resource Identifier: The URI in this subfield may link to an electronic version of the resource described in the record or to any electronic resource that’s related in some way to what’s described in the record.

$0 Authority record control number or standard number: This subfield may contain numbers or text, in addition to URIs. A URI used in $0 will link to a description (like an authority record) of the name or label used in the MARC field.

$1 Real World Object URI: The idea of “Real World Object” (RWO) is new in the library world. Despite the use of the word “object” in this phrase, it also refers to entities that we wouldn’t typically think of as objects, such as people or concepts. A URI used in this subfield points to a description of an entity, rather than a description of a name or label (as a URI used in a $0 would).

$4 Relationship: The subfield $4 has been used for a while in cataloging to carry relationship/relator codes that indicate the relationship of the entity entered in a MARC field to what is being described by the MARC record (Ex. “aut” for “author”). Now, URIs may also be entered in the subfield $4, linking to records that provide further information about these codes.

URIs may also be used to describe “data provenance” in the following subfields: $e, $l, $y, $7. The MARC field being used will determine which subfield is used for data provenance (Remember to consult MARC documentation when choosing a subfield to use). Text may be used in these fields in addition to or instead of URIs. If both text and URIs are used, they are entered in separate subfields (Ex. text in one $7, URI in a separate $7).

Since $0 and $1 and subfields used for data provenance ($e, $l, $y $7) are relatively new (or being used in new ways), a little more explanation of these subfields is in order. This will be the subject of the next post.

This is the second in a series of seven weekly blog posts written by Zahra Gordon, the NHSL Cataloger, which will explain “Linked Data,” an emerging topic in the library field, and how it relates to “Uniform Resource Identifiers (URIs),” which are appearing in subfields of MARC records with increasing frequency.