By-passing taggregations identifies those MARC21 variable data field tags whose level 0 RDF properties, representing individual subfields, can be used generally in data triples and mapping triples without losing information and the semantic coherency of the record. These tags have subfields which are independent of one another, with no need to keep them together if the tag is repeated in a record.

RDF graph of Music format ontology

RDF graph of Music format ontology

This graph is another example of adding MARC fruit to the cornucopia by using the sub-property ladder. The MARC21 property used in the graph is a level 0 element. The MARC21 property’s description is equivalent to the ISBD property’s description, as hinted at in the ISBD scope note, but an unconstrained version is used to avoid the ISBD property’s domain. We could use the Web Ontology Language (OWL) ontological property owl:equivalentProperty to represent the relationship between the properties, but we can also use the rdfs:subPropertyOf property by applying it in both directions. That is, if two properties P1 and P2 are related as P1 rdfs:subPropertyOf P2 AND P2 rdfs:subProperty P1, then P1 owl:equivalentProperty P2 and P2 owl:equivalentProperty P1.

Unfortunately, it is unsafe to use level 0 properties for dependent subfields in repeatable tags in this way, even if a specific record contains only one instance of such a tag. Triples from that record will cluster with triples from another record about the same bibliographical resource, either by sharing the same resource URI or an equivalence link. Taggregations are required to avoid semantic confusion, otherwise we wouldn’t know which “Materials specified” goes with which “Place of publication …” or “Name of publisher …” in the publication statement example given in Taggregations.


By Gordon Dunsire, July 18, 2012, 9:44 am (UTC-5)

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Currently 2 comments

  1. Comment by Gordon Dunsire

    There is no programming here, only markup and simple logic statements.

    However, I think it’s important for librarians to understand some basics of how we get computers to process metadata; cataloguing is the professional core, after all. We need to understand a little of how MARC21 data is processed because instructions are embedded in its encoding, for example indicators for nonfiling characters. I intend to discuss this in a future blog post.

    We also need to understand the meaning of MARC21 data better, to increase return on investment by ensuring that data created and stored is available to the Semantic Web without loss.

  2. Comment by Kathleen Lamantia


    I understand this, but I don’t like it. I went to Library School, not programming school. Dislike!

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