Metadata for Special Collections in CONTENTdm: How to Improve Interoperability of Unique Fields Through OAI-PMH

Abstract

Collection curators develop locally defined unique fields to support local requirements. As per the guidelines of the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH), Simple DublinCore is the minimum requirement for exposing metadata to aggregators. Oftentimes the level of specificity of unique local fields is not translated well to Dublin Core, which may hinder the interoperability of the item metadata record. This paper researched 21 digital collections that were hosted in CONTENTdm. The objective was to explore the use and issues of unique fields in local context and recommend best practices that will increase the interoperability of metadata for special collections. KEYWORDS Dublin Core, metadata, mapping, CONTENTdm, OAI-PMH, interoperability, special collections, metadata standards INTRODUCTIONLibraries wanting to digitize and provide online access to their special collections content must balance the tension between the requirements of local portals providing custom access to such content and the needs of aggregators wanting to provide integrated search and discovery services across special [Hewitt & Panitch, 2003]; we define special collection for this paper as materials that need special care and arrangement, or collections of materials that have been assembled for specific themes.) To deal with unique characteristics and context of special collection items, customized metadata schemes that include uniquely named descriptive attributes are often created for use in local implementations. However external aggregators need to collect and search against standardized or at least normalized descriptive metadata records. This paper examines the use of locally defined unique fields in item-level metadata descriptions of digital surrogates held in 21 collections from 11 CONTENTdm repositories and then examines the issues encountered when trying to map such locally customized metadata records to Simple Dublin Core or Qualified Dublin Core in ways intended to optimize interoperability. CONTENTdm implementations are especially well suited for this sort of examination because the application gives implementers license to add locally defined metadata fields and the freedom to then map or not map these local fields to Dublin Core however the implementer sees fit for purposes of metadata record export. This paper stems in part from a finding described in the article Dublin Core Metadata Harvested through OAI-PMH (Jackson, Han, Groetsch, Mustafoff, & Cole, 2008). As described in this earlier paper, we found that "native metadata records are rich in meaning in their own environment, but lose richness in the aggregated environment due to the mapping errors and misunderstanding and misuse of Dublin Core elements" (Jackson et al., 2008, p. 18). This finding is closely related to a sharable metadata issue identified in a 2006 article by Shreeves, Riley, and Milewicz, that is, that "metadata may be of high quality within its local context, but may be compromised when taken out of this context for var...

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