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The OLE Instance schema is loosely based on the MARC Format for Holdings Data (MFHD) and represents core elements that must be included when describing holdings and items. The schema does not support every MFHD field/subfield but does include additional pieces of information not supported by MFHD. Additionally, the OLE Instance schema has taken some elements traditionally captured with holdings data and moved those to item descriptions. These include elements for describing the location of items (MFHD 852 field and subfields) as well as information relating to how users may access electronic resources (MFHD 865 856 field and subfields). Because the current schema only represents "core" elements, it does allow for the addition of "local" pieces of data via the <extension> element.
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