AboutContainers

From oaibp

Main Page >> Data Provider Implementations

[edit] About Containers

About containers are an optional piece of the OAI protocol that allow a repository to include self-referential metadata about the records themselves (see Section 3.4 of the OAI-PMH Implementation Guidelines). An <about> container may have only one child element. If a data provider needs to provide multiple pieces of information about the item, the about container should be repeated within the record. For example, if there is included both a rights expression and a provenance expression, each of these appears in a separate <about> container.

The <about> container refers to the metadata record not the resource itself.

There are two common uses of the <about> container: the <rightsManifest> and <provenance>. Other information may also be included in the <about> container; however, the contents of an about container must conform to an XML Schema.

[edit] Rights

The following example contains rights information about the metadata record:

    <about>
    <oai_dc:dc xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ 
    http://www.openarchives.org/OAI/2.0/oai_dc.xsd" 
    xmlns="http://purl.org/dc/elements/1.1/" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    
    xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/">
    <publisher>The University of Chicago Library</publisher> 
    <rights>No rights to the use of these metadata are granted except by prior agreement.</rights> 
    </oai_dc:dc>
    </about>

The Rights Expression Specification provides a general framework and an XML schema for stating rights about metadata records. It is a best practice to follow these guidelines in describing rights for metadata at the record, set, and repository level.

If rights statements are included, it is best practice to include them at the record level. The Implementation Guidelines state:

Repository and set level manifests must not be used as a substitute for the inclusion of rights expressions at the record level. The manifests at the repository and set levels provide a convenient way to expose rights expressions associated with those aggregations. Harvesters must, however, refer to the individual records for authoritative rights expressions about the metadata.

One important caveat is that the OAI-PMH does not provide a mechanism for enforcing restrictions or conditions that you place on the use of your descriptive metadata. The data provider should think carefully before attaching restrictions or conditions to the use by Service Providers of the descriptive metadata associated with items. Doing so imposes burdens on service providers who wish to harvest this metadata and incorporate it in a specific service, and therefore can restrict the exposure of resources gained by participating in OAI.

Some data providers use the OAI-PMH to surface metadata for harvesting in a more closed environment. In these cases, a rights statement should be provided relating to use of the descriptive metadata in the records. Within the descriptive metadata section of the record, rights elements should only describe the resource itself and not its metadata.

See also Expressing Rights over Metadata section in the Best Practices for Shareable Metadata.

[edit] Provenance

The about container may also contain a provenance node. A specific schema was created to document record provenance. Provenance containers are generally not added by data providers, but by service providers who are re-exposing harvested metadata via OAI. It is a best practice for Service Providers to add a provenance element to all harvested records, that will be re-exposed through the OAI protocol, in order to ensure traceability of metadata records.

The node should contain the harvesting history of the record, through embedded "originDescription" elements. The following example contains provenance information about the metadata record:

    <about>
    <provenance xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/provenance 
    http://www.openarchives.org/OAI/2.0/provenance.xsd" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns="http://www.openarchives.org/OAI/2.0/provenance">
    <originDescription altered="true" harvestDate="2005-1-15">
    <baseURL>http://oai.lib.uchicago.edu/</baseURL> 
    <identifier>oai:lib.uchicago.edu:AEP-AKS25</identifier> 
    <datestamp>2004-10-28T22:21:25Z</datestamp> 
    <metadataNamespace>http://cicharvest.grainger.uiuc.edu/schemas/QDC/</metadataNamespace> 
    </originDescription>
    </provenance>
    </about>