The Public Broadcasting Metadata Dictionary (PBCore) is:
- a core set of terms and descriptors (elements)...
- used to create information (metadata)...
- that categorizes or describes...
- media items (sometimes called assets or resources).
The PBMD Project spent over two years comparing and contrasting
various metadata descriptors, dictionaries, and schemes in order to arrive
at the smallest set of descriptors or elements that could adequately describe
and catalog the media items produced by Public Broadcasting radio and television
stations that may be shared between stations, regional and national distributors,
independent producers, and even vendors of Digital Asset Management systems.
The PBCore is a "core" because it can actually be
considered a foundation of descriptors used to categorize media items adequately
enough so other interested parties can successfully search for and review
desired media items. The objective is to be able to share media items and give
users complete, well-though-out, descriptions. Good descriptions help end users
know what to expect when they decide to review, play or download a media file.
The PBCore is actually a starter kit and one that satisfies most users. However, as the PBCore is implemented by various communities, we will undoubtedly add optional extensions to the existing set of metadata elements to accommodate specials needs (see Extensions to the PBCore). Metadata descriptors related to the utilization of media items in educational settings is a good example of a relevant set of extensions to the PBCore.
Available free of charge to public broadcasting stations, distributors, vendors, and partners, version 1.0 of PBCore was launched in the first quarter of 2005 and version 1.1 was published in the first quarter of 2007. Please reference the links to Who May Use PBCore and PBCore Licensing for additional information about usage and implementation.
Funded by the Corporation for Public Broadcasting and administered by WGBH/Boston, a well-formed metadata dictionary directly addresses public broadcasting’s mission by making its award-winning content more easily accessible to teachers, scholars, lifelong learners, engaged citizens, and community partners.
Based on Dublin Core: The PBCore is built on the foundation of the Dublin Core (ISO 15836), an international standard for resource discovery (http://dublincore.org), and has been reviewed by the Dublin Core Metadata Initiative Usage Board.
Building a Community of Practice: A metadata dictionary and the situations in which it is applied are not static. Much work has been accomplished in order to define a core set of metadata descriptors for use by Public Broadcasters and their associated communities and partners. However, we are part of an evolutionary process that is building a "Community of Practice" for the uses and applications of the PBCore.
How Many Elements ?
Currently we have 53 elements arranged in 15 containers and 3 sub-containers, all organized under 4 content classes.
A more complete explanation is provided on the PBCore web page entitled Hierarchical Relationships and Interdependencies between Metadata Elements.
The hierarchy of roots, branches, and leaves is alternatively expressed in a data model as "Content Classes,'
"Containers," "Sub-Containers," and "Elements." PBCore has 53 elements arranged in 15 containers and 3 sub-containers, all organized within four content classes.
In the hierarchy of objects in the PBCore Description Document/Master Container, Content Classes are created as "conceptual wrappers" that cluster together a list or structure of thematically-related Elements (metadata fields and their attributes and properties). PBCore maintains four Content Classes as the conceptual wrappers for its various metadata elements:
9 containers; 16 elements
(metadata elements describing the actual intellectual content of a media asset or resource)
4 containers; 7 elements
(metadata elements related to the creation, creators, usage, permissions, constraints, and use obligations associated with a media asset or resource)
1 container; 3 sub-containers; 28 elements
(metadata elements that identify the nature of the media asset as it exists in some form or format in the physical world or digitally)
1 container; 2 elements
(additional descriptions that have been crafted by organizations outside of the PBCore Project. These extensions fulfill the metadata requirements for these outside groups as they identify and describe their own types of media with specialized, custom terminologies unique to their needs and community requirements)
ELEMENT CONTAINERS & SUB-CONTAINERS (aka "branches"):
Elements are objects in the PBCore schema hierarchy that define a metadata field and its values, attributes and properties. An element may be standalone. If several metadata fields are thematically related to each other, they can be bound together under an Element Container. Related elements are subsumed by a larger theme, and should be bound together when data is shared (particularly if an Element Container is a repeatable description with multiple instances of its related Elements). Examples of related Elements bound within a Container are *title* and its associated *titleType*, that are bound together by the Element Container *PBCoreTitle*. Within hierarchical structures, a Container may house Sub-Containers, which themselves bind together related Elements. In PBCore, there are Sub-Containers found within the Content Class PBCoreInstantiation.
ELEMENTS (aka "leaves"):
Elements are objects that define a metadata field and its values, semantics, attributes, and properties (for a list of the attributes defined for PBCore elements, see our web page PBCore Element Attributes). An Element is the actual "thing" that carries the descriptive metadata about a media item, such as a title, a date, keywords, rights information, mime types, media types, etc. The metadata elements are what a cataloger interacts with (creating descriptions) within a cataloging tool or asset management system.
To review detailed information about each element,
a good starting point is to access the PBCore User Guide.