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Schema Endorsement: how and why

The external schema endorsement process

The endorsement process for an external schema may be initiated either by the METS Board, or by the community that develops and/or wishes to use the particular schema. Users should not assume that schemas not appearing the list of endorsed schemas are not suitable for use in METS. The METS Board may simply not have reviewed such schemas yet. Requests for such a review should be submitted to the METS list.

The purpose of external schema endorsement

METS does not specify an XML vocabulary and syntax for descriptive and administrative metadata. The METS dmdSec, techMD, sourceMD, digiprovMD and rightsMD elements can reference external metadata in any digital format, or contain such metadata either in base64 encoded format or in XML format. XML encoded metadata used in these METS contexts can either conform to an external schema or to no schema.

To encourage the use of community recognized standards, the METS Editorial Board endorses schemas that it feels are especially suitable for use in governing XML metadata appearing in or referenced from the METS dmdSec, techMD, sourceMD, digiprovMD and rightsMD elements. Such endorsement indicates:

• 1. The endorsed schema represents the consensus of a community of need.
• 2. The schema has achieved production status.
• 3. The schema is maintained for use by an organization representing the community that developed the schema; and is made publicly available by this organization from an official, web-accessible location.
• 4. The METS Board has reviewed the schema and satisfied itself that it can function effectively in a METS context.

The relationship of the MDTYPE attribute to endorsed external schema

The METS schema includes an MDTYPE attribute on its mdRef and mdWrap elements that is governed by a controlled vocabulary list (or "enumeration" in XML schema terms). While the types of metadata that are represented by endorsed schemas should all be represented in the MDTYPE controlled vocabulary list, the list may also include metadata types represented by schemas that have not been endorsed and metadata types that are not represented by schemas at all. The controlled vocabulary list is simply intended to reflect commonly used metadata types, and to facilitate the sharing of METS files among institutions. The MDTYPE value list is not closed, and METS users may submit requests for additions to the list on the "METS Schema Revisions Requests" page of the METS wiki. METS users can also record types of metadata not represented in the MDTYPE controlled vocabulary list by specifying "OTHER" as the MDTYPE value and then recording the specific type of metadata in the uncontrolled OTHERMDTYPE attribute.

The METS Board is currently considering options for managing its controlled vocabularies outside the METS schema itself. It is difficult to anticipate the metadata types that METS users may want to record in the MDTYPE attribute, and thus keep the associated controlled vocabulary lists current. The METS Board is seeking the best way to keep its controlled vocabularies current and useful while still encouraging consistency in the their use. Suggestions and comments may be directed to the METS list.

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