extensionWrap serves as a container for the elements extensionElement, extensionValue, and extensionAuthorityUsed.

extensionWrap can be contained by the elements pbcoreExtension, instantiationExtension, or essenceTrackExtension.

Usage: required within pbcoreExtension, instantiationExtension, or essenceTrackExtension, if extensionEmbedded is not used; cannot be used with extensionEmbedded.  Repeatable. 


  • source – optionalAttribute source provides the name of the authority used to declare the value of the element. Different elements will use the source attribute slightly differently. For example, identifier source (required) should be the name of the organization, institution, system or namespace that the identifier came from, such as “PBS NOLA Code” or an institutional database identifier. For other elements, this might be the name of a controlled vocabulary, namespace or authority list, such as Library of Congress Subject Headings. We recommend a consistent and human readable use.
  • ref – optionalUse attribute ref to supply a source’s URI for the value of the element. Attribute ref can be used to point to a term in a controlled vocabulary, or a URI associated with a source.
  • version – optionalAttribute version identifies any version information about the authority or convention used to express data of this element.
  • annotationoptionalAttribute annotation includes narrative information intended to clarify the nature of data used in the element. Can be used as a notes field to include any additional information about the element or associated attributes


extensionWrap contains the following subelements:

  • extensionElement – required. The element extensionElement provides metadata descriptions from metadata dictionaries and schemas outside of PBCore.
  • extensionValue – required. Use extensionValue to express the data value of the label indicated by extensionElement.
  • extensionAuthorityUsed – optional. The element extensionAuthorityUsed identifies the authority used for the extensionElement.


Submit any issues or suggested changes for future schema iterations by creating a ticket in our Github repository.