The navigation in an ever-changing overloaded bibliographic universe that preserves the contextual semantics of the bibliographic descriptions largely depends on the control of content relationships and bibliographic families. According to Tillett  content relationships exist between different bibliographic entities and can be considered as a sequence of intellectual/artistic content; as this continuum gets distant from the original parent, the relationship becomes remote. The term bibliographic family is defined as ‘a set of related bibliographic works that are somehow derived from a common [parent]’ . Library conceptual models include constructs to describe and control relationships and bibliographic families. The identification of bibliographic families and the clustering of all related entities shall enable future library catalogs’ navigation functionalities. The preservation of bibliographic families maintains the information that two or more Works originate from a common progenitor. Hence, successful mappings between different conceptual models presuppose the preservation of content relationships and bibliographic families after data transformation [3–5].
This paper is based on  and examines if and how information about content relationships and bibliographic families may be preserved in mappings from FRBR to BIBFRAME. The cases of a Work with a single Expression, as well as bibliographic family cases e.g. Work with multiple Expressions and Works with derivative relationships are studied and some interesting findings have been derived. Mapping content relationships and bibliographic families
Work with a single Expression The simplest and the most frequent bibliographic case  is a Work with a single Expression and a single Manifestation, e.g. a monograph (book) in a language. The mapping for this case seems straightforward (Figure 1). The FRBR path Work-is realized through-Expression is mapped to the bf:Work class, while the rest constructs of the path are mapped 1:1. More precise mappings may be developed for each of the 10 subclasses of the BIBFRAME Creative Work class and for the 5 subclasses of the bf:Instance class.
Fig. 1. Mapping from FRBR to BIBFRAME representation pattern for a Work with a single Expression.
The exploitation of (a) the attributes of the FRBR Expression and Manifestation entities and (b) controlled vocabularies from the Library of Congress Linked Data Service or ISBD vocabularies to specify the values of the attributes improve significantly the semantic precision of the mapping rules. For instance at the Expression level, we have identified the form of expression attribute and we used the LC Content Types Scheme for its values to enable precise mappings for all bf:Work subclasses. In some cases these values may even determine the mapping to a bf:Instance subclass (see Figure 2). Furthermore, at the Manifestation level, we have identified the form of carrier attribute and used the LC Carriers Scheme.
Fig. 2. Mapping from FRBR to BIBFRAME a detailed representation pattern for a Work with a single Expression.
The path Expression-form of expression-contentTypes: tactile text triggers mapping to bf:Work and bf:Instance subclasses. The utilization of controlled vocabularies for interoperability reasons demands both their multilingualism and their representation in RDF. Therefore, cataloging should be performed taking into account the collaboration and data reusability principles.
Work with multiple Expressions In the case of mappings from an FRBR Work with multiple Expressions to BIBFRAME, two instances of the bf:Work class are generated. However the semantics regarding the origination of the two instances of the bf:Work class from the same Work (intellectual idea) are lost (Figure 3).
Fig. 3. Mapping from FRBR to BIBFRAME representation pattern for a Work with a single Expression. After mapping, both parent and bibliographic relationship are lost.
Derivation - translation Literal translation is represented in FRBR by relating two or more Expressions of the same Work with the has translation relationship (upper part of Figure 4). After mapping to BIBFRAME, the content relationship between the two Expressions is preserved in the two bf:Works. The information that the bf:Work instances have the same progenitor (Work) is not preserved though (Figure 4).
Fig. 4. Mapping from FRBR to BIBFRAME representation pattern for the translation case.
In order to preserve information about the common parent, an additional Expression-agnostic bf:Work instance will be created (bf:Work with the long dash-dot outline in Figure 5). Then this additional bf:Work instance will be linked with the others bf:Work instances using the bf:hasExpression property (also depicted with a long dash-dot line). This Expression-agnostic bf:Work cannot have any bf:Instances but it can serve as a the parent for all bf:Works that somehow derive from it.
Fig. 5. Mapping from FRBR to BIBFRAME representation pattern for the translation case. The bf:Work with the long dash-dot outline has been added in the mapping to preserve the parent bf:Work of the Odyssey bibliographic family.
Adaptation is represented in FRBR, either between Works, or between Expressions of different Works. This case demonstrated similar results with the translation case: content relationships are preserved, the parent is lost and the addition of Expression-agnostic bf:Work preserves information about the bibliographic family.
Fig. 6. Mapping from FRBR to BIBFRAME representation pattern for the adaptation case. The Expression-agnostic bf:Work serves as the parent bf:Work of the Odyssey bibliographic family.
One key finding has been that relationships between members of a bibliographic family are preserved in BIBFRAME when FRBR Expressions are related. Moreover, the parent Work is not always represented in BIBFRAME after mappings.
This study uses a limited set of cases and data. A follow-up study shall use a bigger dataset and test more cases; it will also compare the transformation using existing transformation tools to evaluate their degree of preservation of bibliographic relationships after mappings. Interesting findings are also anticipated for testing IFLA LRM to BIBFRAME and the opposite mappings.
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