Evidence Summary
Digital Libraries that Demonstrate High Levels of Mutual Complementarity
in Collection-level Metadata Give a Richer Representation of their Content and
Improve Subject Access for Users
A Review of:
Zavalina, O. L. (2013). Complementarity in subject metadata in large-scale
digital libraries: A comparative analysis. Cataloging
& Classification Quarterly, 52(1),
77-89. http://dx.doi.org/10.1080/01639374.2013.848316
Reviewed by:
Aoife Lawton
Systems Librarian
Health Service Executive
Regional Library & Information Service, Dr. Steevens’ Hospital
Dublin, Ireland
Email: aoife.lawton@hse.ie
Received: 29 Jul. 2014 Accepted: 14 Oct. 2014
2014 Lawton.
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Abstract
Objective – To determine how well
digital library content is represented through free-text and subject headings.
Specifically to examine whether a combination of free-text description data and
controlled vocabulary is more comprehensive than free-text description data
alone in describing digital collections.
Design –
Qualitative content analysis and complementarity comparison.
Setting – Three large scale
cultural heritage digital libraries: one in Europe and two in the United States
of America.
Methods – The researcher retrieved
XML files of complete metadata records for two of the digital libraries, while
the third library openly exposed its full metadata. The systematic samples
obtained for all three libraries enabled qualitative content analysis to
uncover how metadata values relate to each other at the collection level. The
researcher retrieved 99 collection-level metadata records in total for
analysis. The breakdown was 39, 33, and 27 records per digital library. When
comparing metadata in the free-text Description metadata element with data in four controlled vocabulary
elements, Subject, Geographic Coverage, Temporal Coverage and Object Type, the
researcher observed three types of complementarity: one-way, two-way and
multiple-complementarity. The author refers to complementarity as “describing a
collection’s subject matter with mutually complementary data values in
controlled vocabulary and free-text subject metadata elements” (Zavalina, 2013, p. 77). For example,
within a Temporal Coverage metadata
element the term “19th century” would complement a Description
metadata element “1850–1899”
in the same record.
Main Results – The
researcher found a high level of one-way complementarity in the metadata of all
three digital libraries. This was mostly demonstrated by free-text data in the
Description element complemented by data in the controlled vocabulary elements
of Subject, Geographic Coverage, Temporal Coverage, and Object Type. Only one
library demonstrated a significant proportion (19%) of redundancy between
free-text and controlled vocabulary metadata. An example of redundancy found
included a repetition of geographic information in both a Description and
Geographic Coverage metadata elements.
Conclusion – The author
reports high levels of mutual complementarity in the three cultural heritage
digital libraries studied. The findings demonstrate that collection-level metadata
which includes both free-text and controlled vocabulary is more representative
of the intellectual content of the collections and improves subject access for
users. The author maintains that there is no standard for collection-level
metadata descriptions, and that this research may contribute to best practice
guidelines in this area. It is unclear whether the
digital libraries studied had written policies in place on how to describe collections and if those policies were adhered to in practice. The author expresses a need for further research to
be conducted on collection-level metadata in other domains, such as science and
interdisciplinary digital libraries, and on other scales (e.g., regional or
state collections) and geographic regions beyond Europe and the United States.
Commentary
Although there is an abundance of general research and
literature on metadata, digital libraries, interoperability, and standards,
there is little specific research on complementarity of collection-level
metadata. This research highlights this gap and adds value to the current body
of research on this topic.
The methods of data collection and presentation of
results score high on Glynn’s critical appraisal checklist (Glynn, 2006). This
work builds on a previous study by the same author, which compared the
free-text Description metadata field in multiple digital libraries (Zavalina,
2011). The current work extends the analysis to include three digital libraries
of similar content and size and the comparative analysis of free-text
Description element with four controlled vocabulary subject metadata fields.
The sample size of metadata records from each library is similar, making the
analysis sufficiently precise. Consent was obtained from developers of two of
the digital libraries who agreed to provide the records for the content
analysis. There is a detailed description of the level of comparative analysis
carried out. However, there is no description of any tools that may have been
used to compare the metadata records and retrieved digital content samples. A more
detailed description of the methodology used would have been useful.
The results are well presented with five figures that
visually demonstrate the level of complementarity between metadata elements.
The extensive descriptive detail provided by the author enables further
replication of this study on other digital library collections. The author
thanks individuals at two universities for feedback on her study; however it is
unclear whether the method of the content analysis used has been externally validated
beyond this feedback. The author refers to the importance of complementarity of
metadata in digital collections as an enabler of subject based access to
collections. This study would be strengthened with the inclusion of evidence
about how users of cultural heritage collections browse or search collections
by subject.
Based on the evidence presented in this paper, digital
library managers, repository managers and cataloguers should consider the
collection-level metadata that they are currently implementing and whether this
is something that needs attention. Specifically, the potential for levels of
redundancy observed in this study is an important finding. Cataloguers could
save time by avoiding entering duplicate data, such as identical geographic
information in both Description and Geographic Coverage elements. As the growth
of digital library collections is set to continue, adherence to standards of
metadata descriptors and best use of descriptive content including free-text
and controlled vocabulary elements will become ever more important to
discoverability. The author signposts two guidelines of relevance to
cataloguers: the Framework of Guidance
for Building Good Digital Collections established by NISO, and the Guidelines for Digital Libraries being
prepared by the International Federation of Library Associations and
Institutions in conjunction with the World Digital Library Project.
References
Glynn, L. (2006). A critical appraisal tool for library and information
research. Library Hi Tech, 24(3),
387-399. http://dx.doi.org/10.1108/07378830610692154
Zavalina, O. L. (2011). Free-text collection-level subject
metadata in large-scale digital libraries: A comparative content analysis. In
T. Baker, D. I. Hillman, & A. Issac, (Eds.), Metadata harmonization: Bridging languages of description. Proceedings
of the DCMI International Conference on
Dublin Core and Metadata Applications (pp. 147.157). DCMI. Retrieved from http://dcpapers.dublincore.org/pubs/index