The OLAC metadata standard OLAC-Metadata follows the generic resource description standard known as "Qualified Dublin Core" DCQ. In order to meet the specific needs of the language resources community, the OLAC metadata standard incorporates an extension mechanism that makes it possible to describe language resources with greater precision. The mechanism uses the xsi:type attribute to override the basic definition of a Dublin Core metadata element with a definition that has a more precise semantics. For instance, the following subject description,

can be formally identified as pertaining to a language and as relating to the specific language identified by the ISO 639-3 code ybb by employing an OLAC extension: as follows:

Details on how the extension mechanism works may be found in the last two sections of OLAC-Metadata.

Any party may develop a metadata extension and use it in OLAC metadata records. When an extension is proven to work and is judged to have wide relevance across the language resources community, then it may be put forward to the community as a recommended best practice. If, after following the process described in OLAC-Process, the community reaches consensus that the extension should indeed be used where applicable by all OLAC member archives, then the extension achieves the status of an OLAC Recommendation.

This document provides the complete list of all extensions that have been adopted as OLAC Recommendations. Each extension is described in terms of a title and the following six descriptors:

Name

The symbolic name that is used as the value of the xsi:type attribute to indicate that the extension is being used in a metadata element.

Date

The latest revision date of the extension or its controlled vocabulary.

Applies to

The Dublin Core elements with which the extension may be used.

Description

A summary description of what the extension is used for.

Documentation

A link to a complete document that defines and exemplifies the extension. If the extension involves a controlled vocabulary, the document should also enumerate and define the terms of the vocabulary.

Schema

A link to the XML schema that formally defines the extension.

The Open Language Archives Community recommends that all participating data providers use the following metadata extensions for describing language resources whenever they are applicable: