Mappings
Index to Mappings to Other Metadata Standards
Current Version of PBS DLL Metadata is 1.2
Index of Available Mappings to and from PBS DLL Metadata
Below are listed existing and future mapping efforts to and from the PBS DLL Metadata Dictionary and other significant metadata standards. To review a specific mapping, click the "arrow sign" 
pointing from a "Source Metadata Dictionary" to a "Target Metadata Dictionary."
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|---|---|---|
| PBS Digital Learning Library | |
PBCore |
| PBCore | |
PBS Digital Learning Library |
| PBS Digital Learning Library | |
Dublin Core |
| Dublin Core | |
PBS Digital Learning Library |
| PBS Digital Learning LIbrary | |
American Archives Project |
| American Archives Project | |
PBS Digital Learning LIbrary |
| PBS Digital Learning Library | |
Marc 21 |
| Marc 21 | |
PBS Digital Learning Library |
| WGBH Teachers' Domain | |
PBS Digital Learning Library |
| Maryland Public Television Thinkport | |
PBS Digital Learning Library |
| Utah Education Network Digital Media Service |
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PBS Digital Learning Library |
About Metadata Mappings and Data Crosswalks
A metadata standard is created in order to identify and document (in an organized and logical manner) how content, knowledge, and media are to be described. Media is defined broadly as audio, video, text, images, animations, interactives--virtually any item conveying a message, theme, or affect.
Metadata descriptions
Metadata descriptions frequently organize themselves into four major categories or classes:
- the actual intellectual content of an item
(what's it about?) - property and usage rights over an item
(who owns it, manages it, and what are the use permissions, restrictions, and obligations) - format information about an item's physical or digital forms
(instantiations, formats, technical attributes & configurations) - utilization and audience appeal
(target audiences, preferred integrations into teaching methods, lesson planning)
Descriptions of media items are expressed through metadata "elements." An element is a named placeholder for a very specific type of information, e.g., a title, an author's name, a country, a creation date, a set of keywords, a learning objective, an expiration date, etc.
Different metadata standards
Different metadata standards exist in order to serve the needs of particular user communities, such as public broadcasters, TV program listings, libraries, medical practitioners, artists, global positioning data, museum collections, image repositories, statistical and social research, educational applications, to identify a few.
In most cases, each metadata element that is employed in a metadata standard is itself documented with a consistent set of properties or attributes for identification and definition. The PBS DLL, like many others, is based on the properties that are outlined in the ISO/IEC 11179: Specification and Standardization of Data Elements and is expressed in half a dozen published documents and drafts. Technically speaking, the PBS DLL Metadata is considered to be "cognizant of ISO/IEC 11179." To learn more about the data element properties that PBCore employs, reference this page in our website:
Review Introduction to Metadata > Defining Elements: Attributes
Sharing Metadata Information
What happens when one community desires to share metadata information entered in its systems with another community that maintains its own metadata standard? In an ideal data world, each metadata element from the "source" metadata standard could be paired with a similar metadata element in the "target" metadata standard, and the data would be transferred.
Unfortunately, such a pure one-to-one pairing or "harmonization" is rare. Although each standard may use a common method to express the properties of its metadata elements, the actual data held within the element may not "crosswalk" or "map" without first undergoing translations and transformations.
The following quote was extracted from an excellent article entitled "Issues in Crosswalking Content Metadata Standards." It is published through NISO, the National Information Standards Organization, and authored by Margaret St. Pierre of Blue Angel Technologies, Inc. and William P. LaPlant, Jr., of the U.S. Bureau of the Census Statistical Research Division.
A crosswalk is a specification for mapping one metadata standard to another. Crosswalks provide the ability to make the contents of elements defined in one metadata standard available to communities using related metadata standards. Unfortunately, the specification of a crosswalk is a difficult and error-prone task requiring in-depth knowledge and specialized expertise in the associated metadata standards. Obtaining the expertise to develop a crosswalk is particularly problematic because the metadata standards themselves are often developed independently, and specified differently using specialized terminology, methods and processes. Furthermore, maintaining the crosswalk as the metadata standards change becomes even more problematic due to the need to sustain a historical perspective and ongoing expertise in the associated standards.
http://www.niso.org/publications/white_papers/crosswalk/
Harmonizing Elements from Different Standards
When harmonizing metadata elements from different standards, there are several points of intersection where collisions, rather than smooth merging, may occur.
Matching Semantic Definitions
An element in the source standard may not find a companion element in the target standard because the definition, semantics, or meaning for elements are different. With such a mismatch, a descriptor may not translate well.
Matching Element-to-Element Relationships
Suppose the source standard uses separate metadata elements to identify the (1) Last name of a person, (2) First name, (3) Middle name, and (4) Credentials for an individual. What if the target standard only employs a single element to contain all of a person's names, prefixes and suffixes? How do the "many" elements of the source map to the "one" element in the target? There is a "many-to-one" mismatch. Likewise, there may exist a "one-to-many" element mismatch between the source and target standards. Furthermore, one standard may contain extra elements and descriptors that cannot even be paired with the other system.
Matching & Converting Content
The properties for a metadata element may define or restrict its contents by...
- data types (e.g., text, numeric, string, date, etc.),
- ranges of values, or
- data refinements derived from the use of various authorities, controlled vocabularies, or specific syntaxes for the presentation of the data (e.g., keywords separated by semi-colons).
repeatability of the element in order to express multiple values or descriptions- mandatory or optional usage of the element when entering values.
Even though a metadata element from a source standard may semantically match an element in a target standard, the rules by which the actual data entered in the element may differ between the systems. The mismatch may be resolved by some form of conversion or data reformatting. Consistency in how data was originally entered is key to formulating conversion utilities or crosswalks.
Matching Single vs. Multiple or Compound Data Objects
Many asset management systems and databases allow the relationships between several data records/media items to be expressed. For example, a video program might have a transcript (text document), brochure (pdf), DVD (non-digital medium for order fulfillment), and other items associated with it. If an end user searches for the video program, the search results report the related media items as well. These associated/related items are often housed as a "multiple" or "compound" data object. Many databases actually refer to them as "container fields." If the source and target metadata system use different methods to identify and report multiple or compound objects, then a mismatch in mapping occurs.
Matching Hierarchical and Flat Metadata Standards
Some metadata standards, like IEEE-LOM (Learning Object Metadata), use a very hierarchical structure to organize the relationships between metadata elements. These relationships can often become quite complex. PBCore v1.1 uses a hierarchical set of element interdependencies. Other standards, such as the PBS DLL and Dublin Core, are flat in nature, with no implied or expressed hierarchy. Trying to pair metadata elements between a hierarchical and a flat system can be troublesome.
Exporting and Importing Metadata
For an important discussion on exporting and importing metadata descriptions using XML and XML Schema Definitions as the data bridge, reference our web page Exchanging Metadata > XSD: XML Schema Definition.
To learn more about an important initiative related to harvesting metadata from compatible information systems, link to the web page for the OAI: Open Archives Initiative. The OAI provides a protocol for metadata harvesting that is an application-independent framework.
