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Some Identifers used by the NSDL

There are at least three key values that are all called 'identifier' in the current NDR/OAI parlance.

OAI identifiers

The NSDL creates these for identifying the OAI items in the repository. The OAI identifiers use a different scheme for old MR and new NDR OAI services - even though they contain the same metadata. Our old MR OAI identifiers were problematic because they used part of their source's identifier - which was often problematic. The new ones are based on a much simpler scheme.

Example old-style (MR) OAI identifier:

Example new-style (NDR) OAI identifier:

Notice that OAI identifiers always start: oai:... The specification for OAI identifiers is here:

NDR Handle identifiers

The NSDL creates these for uniquely identifying ALL objects within the NDR. These objects include Metadata, and Resource objects, as well as others. The handle of an object is used for many NDR method calls. These are similar to, but NOT the same as an OAI identifier from the NDR.



Identifiers used in metadata items to identify a resource in the wild

These are the things that metadata is supposed to be about. They are found within a metadata record and are usually, but not always, described by the metadata element <dc:identifier>. They are usually, but not always URLs. The ingest process of the NSDL repository uses for these identifiers to construct [ObjectTypes Resource Objects] within the NDR.

Examples (included in snippets of metadata for context):

 <dc:identifier xsi:type="dct:URI">[269:NAN]2.0.CO;2</dc:identifier>
 <dc:date xsi:type="dct:W3CDTF">1960-12</dc:date>
 <dc:language xsi:type="dct:RFC3066">en-US</dc:language>
 <dc:identifier xsi:type="dct:URI">[0964:COTFAM]2.0.CO;2</dc:identifier>
 <dc:language xsi:type="dct:RFC3066">en-US</dc:language>
 <dc:identifier>Citation: Abstr. Appl. Anal. 2003 (2003), Number 13, 757-768</dc:identifier>
 <dc:type xsi:type="dct:DCMIType">Text</dc:type>

Note: The preceeding three examples contain two dc:identifier references that are URLs, and two that are not. The metadata represented above would generate four distinct [ObjectTypes Resource Objects] within the NDR, but only three [ObjectTypes Metadata Objects].

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