RecordGranularity

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Note: Summary of best practices added. Jenn Riley 10/11/05

[edit] Granularity of Description

[edit] Summary of Best Practices

• Expose metadata records at the smallest level of granularity appropriate for the resources being described.
• Do not expose individual metadata records for digital objects that are only subordinate parts to a single item.

Data providers should expose metadata records at the smallest level of granularity appropriate for the resources being described. For many resources, this will be at the single-item level. Item-level description is most appropriate for resources whose individual characteristics are of primary importance to end-users, where the differences between a resource and other similar resources are significant. Eprints, published materials, letters, photographs, and paintings are some categories of resources for which item-level description is most likely useful. For resources in these categories, the creator and subject, for example, are important but not necessarily the same as creator or subject for other resources in the repository. It is therefore important to provide records for individual resources to allow end-users to locate and access them.

There are other types of resources for which item-level description is not as useful. These resources include those in which a creator or manager has organized or grouped component parts into a coherent whole that serves as the resource of interest to end-users. Learning objects, web sites, and some types of archival collections are categories of resources for which records describing groups of items might be most useful. For these resources, describe the characteristics of the group that would be of primary interest to the end-user.

Example of an archival collection not described at the item level:

   <title>Christian Concern for Southern Africa</title>
   <creator>Christian Concern for Southern Africa</creator>
   <description>Records, 1966-1993, of Christian Concern for Southern Africa (CCSA), 
   comprising papers on the constitution of the CCSA; its Executive Committee 
   and Annual General Meeting papers; finance papers and examples of many of 
   CCSA's publications and reports. Also included are files of correspondence between
   CCSA and churches and religious organisations, affiliated support groups and British
   companies in South Africa. Papers also include those of the Oil Working Group, which 
   contain material on the Royal Dutch/Shell Group; the mass lobby of Parliament 
   (17 June 1986) for 'Sanctions against Apartheid' organised by CCSA; and the Ethical 
   Investment Research Service, founded as an independent offshoot of CCSA.</description>
   <publisher>School of Oriental and African Studies</publisher>

See DC Aim25 Collection 1 for the compete record from which this example was taken.

On the other extreme, it is rarely useful in the OAI environment to expose records for multiple digital items that together make up a complete resource, for example, individual page images in a digitized book. It is best practice that, unless each component part has significantly different descriptive information, metadata should instead be exposed for the intellectual resource (e.g., the book), and access to the individual parts (e.g., the pages), if they have been digitized, should be supplied through navigation in the data provider's local environment. The same is true for collections of individual resources that vary only in a very small and, for the end-user, insignificant way; for example, a collection of coins that vary only in their accession number. These should be described as a collection and access to the individual items should be made available within the data provider's local environment.

See also the section on Best Practices for Sets in the Best Practices for Data Provider Implementations for information on using the OAI set capability to create logical groupings of records in an OAI repository.