A-1.4 Why aggregate metadata?


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Why share content? Sharing brings together distributed collections, supports one-stop searching, benefits users and increases the exposure of collections. Lorcan Dempsey [i] uses the phrase ‘in the flow’ to describe how to get content ‘out’ into the world where users will find it.
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There are two main ways to share metadata: federated search and metadata aggregation. In the federated search model in which a user searches from a single central location, the query is sent to distributed databases and the results are sent back to the central query source to assemble, or render, the results. Z39.50 and Search/Retrieval via URL (SRU) are examples of standards used in federated searches.
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Alternatively, the metadata aggregation model pulls metadata from many sources into a single location. Search engines, union catalogues, OAI-PMH, RSS and ATOM [ii] do this . It provides an opportunity to enrich and standardise the metadata. Once users discover a resource they are usually redirected to the original source of the item.
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In a recent book about social media and content, Blossom (2009) states that the aggregation business model is only getting stronger with the popularity of social media and social networks. We are moving toward ‘highly focussed aggregation of content for very specific audiences….’
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Swann and Awre (2006), having described a proposed aggregation model for facilitating end-user services across repositories, then outlined how the aggregation model meets the needs of the respective user-groups identified in their research. This table is reproduced here with permission as it is a useful summary, encompassing the stakeholders mentioned elsewhere in this scoping study.
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User Group Benefits of aggregation model
For repository managers (service providers):
  • Aggregations relieve repository managers from the maintenance of direct services (albeit that these may still be required depending on circumstances) and dealing with end-user services themselves.
  • End-users can be directed straight to the required resource from an aggregator rather than through the repository front-end.
  • Aggregations offer an alternative route for enhancing metadata held within a repository through feeds back from aggregator of enhancements carried out at aggregator level.
  • The aggregator may address authentication and authorisation issues where required as trusted intermediary.
  • Aggregation by a third party service can facilitate preservation through appropriate metadata provision and/or content storage.
  • Repository maintains control over content whilst releasing metadata (though note possibility of exposing content for aggregation as well).
For end-users as readers and searchers:
  • Aggregations offer breadth of access across many repositories, relieving end-users from accessing each one individually.
  • Aggregations can offer control and personalisation of content access (e.g., using RSS) allowing the end-user to determine which sources they have access to.
  • Aggregations offer the capability of developing specific D2D services for specific end-user groups.
End users as content providers:
  • Aggregations provide exposure for content providers to make their work available widely.
  • Such exposure can be focussed around related materials such as aggregations offering subject entry points.
  • Aggregators can provide preservation and metadata enhancement capabilities to support the long-term storage of and access to the content.
Content aggregators
  • Aggregators can offer added-value services of their own to enhance aggregated metadata and supply this back to the repositories concerned.
  • Aggregators can also use the amalgamated collections as the basis for analysis, such as text and data mining.
  • Aggregators can provide a brokering role to facilitate access by end-user services (possibly including a marketing element).
Meta-users:
  • Aggregations can offer a single point of information for statistics about access and downloads of data.
  • At an individual repository level aggregations can offer a benchmark for comparative purposes to support repository management.
Entrepreneurs:
  • Aggregations provide a single point of access to multiple sources of research and other materials to aid discovery.
  • Aggregations also provide suitable collections of materials for possible commercial exploitation through the building of value-added services on top.
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Further benefits to aggregating metadata for learners and teachers, outlined by Pitts and Sharp (2003), include:
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  • New ways to access information to enhance learning and teaching.
  • That resources relevant to a topic can be categorised by the type of resource.
  • Multiple routes through a resource can be tailored to a students’ preferred learning style.
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Shreeves and Kirkham (2004) described some of the experiences of tutors using an aggregation of metadata delivered through a portal: ‘The testers generally agreed that the UIUC portal was useful for pre-screening collections of digitized resources and providing both collection descriptions and links. They stated that this vetting of available sites saved them time and effort and enabled them to look for primary source materials in context-specific, specialized collections, increasing the chance that they might find useable items’.
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Further argument for aggregating metadata of image and audio-visual collections comes from the pressing need for preservation. The Tracking the Reel World (2008) survey concluded: ‘This survey makes overwhelmingly clear that there is a huge amount of valuable audiovisual material spread over a large number of institutions that are at the moment not in the best position to guarantee long-term access and preservation’.
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The survey went on to state: ‘The conditions under which analogue recordings are kept are often not adequate, and lack of resources, equipment and expertise make it a giant step for mixed-media institutions with small minority collections to move them into the digital domain…
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The interest in sound and moving image materials has turned out to be immense now that they can be accessed easily, and there is every reason why audiovisual materials in small mixed-media collections should be high on the list of candidates for digitization. However, the institutions that hold them cannot be expected to carry out this task on their own…’
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Tracking the Reel World identified 0.9 million hours of film, 9.4 million hours of audio, and 10.5 million hours of video, the majority of which is concentrated in a handful of extremely large collections (national audiovisual archives, broadcasters, deposit libraries). However, many of the collections also recorded in the survey were small or very small; their results show that about 65% of film and around 40% of audio and video collections consist of no more than 500 hours of materials.
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A-1.4.1   Uses and Users of Aggregation

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Little has been written on how users interact with collections of aggregated metadata. However, several studies have investigated the challenges of aggregating metadata for both internal processes and end-users. Liu et al. (2002) documented the problems of heterogeneous metadata in the ARC cross archive searching service. They suggested that through a series of interactions with subject terms culled from harvested collections, a user could select the appropriate collections in which to search. Arms et al. (2002) and Shreeves et al. (2003) noted how variations in metadata authoring practices and consistency of metadata records challenge service providers’ abilities to build consistently searchable systems. Issues mentioned by these authors included the variation in elements and vocabularies used and the depth of description.
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Aggregations of metadata have made it easier to search, relate and sell books on the internet:
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“the online aggregation of book metadata brought about by centralized Internet bookselling was a boon for publishers, who saw an unprecedented surge in sales of the backlist titles that they no longer promoted through established channels; it was equally an advantage for scholars seeking out those obscure backlist titles. Readers, for the first time, had at their disposal an easy way to search across a comprehensive, cross-publisher database of available books and complete a purchase. The digital medium has made published information easier to disseminate, search, and sell, and metadata plays a critical role in these advantages.[iii]
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[i] http://orweblog.oclc.org/archives/000688.html
[ii] See standards section of this appendix for more detail on these standards
[iii] http://www.niso.org/standards/resources/Metadata_Demystified.pdf

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