CECSpecialistI
commented
2 years ago From my email exchange with Adam: I just don't know how this would be mapped to RDA. Depending on the field link type, you have different kinds of relationships. I don't think $8 has been used in MARC bibliographic records in the Anglo-American cataloging community, so I don't think we'd ever have to convert it. But other communities may make use of it (the Germans do all sorts of things we simpletons in OCLC don't bother to do).
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The most immediate thought I have is to map to related entity of RDA entity or one of its narrower elements.
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I think this is a subfield that is outside of RDA. It would be interesting to see if it has been used in OCLC at all. We do use it in the holdings format. If it's mapped, it would have to be some kind of relationship, but I think these relationships would better be expressed in work records most of the time.
Numeric and Control Subfields