John Graybeal

Moving Between Standards (Crosswalking)

Crosswalks are human- or computer-readable documents that map metadata elements between different metadata standards.

Crosswalks can apply to content standards, vocabularies, or both. An automated crosswalk process may take an instance of a metadata description that is presented in a particular format and change the format and element names and the values within those elements (i.e., the vocabulary) to meet the requirements of the second standard.

Selecting a Standard

Metadata standards are formal specifications of how metadata should be expressed, and following an accepted metadata standard helps ensure that data are appropriately described for later discovery and reuse. But there are many standards, and not all standards are appropriate to a particular project. In choosing a standard from the hundreds available, it is important to evaluate options based on project needs with the goal of creating an interoperable system.

Metadata Standards

A metadata standard is a model for metadata storage that is approved by a recognized standards organization, such as ISO or FGDC. Metadata standards specify the kinds of information required to describe data. When a metadata document conforms to a standard, it is considered formal metadata. Standards can provide very specific information about details such as values to be provided and how to technically present the metadata.

Metadata standards can be of either or both of these two general types:

Metadata Standards vs. Metadata Specifications

Some confusion exists about the use of the words standard and specification when applied to metadata. On the MMI site, we maintain the following distinction:

Harmonization of Metadata Standards

Metadata standards are often described in terms of element names and definitions. A standard defines the rules for how the metadata are structured and also the appropriate content for the various elements.

However, different standards can be stated in different ways. In other words, a particular standard (the source standard) doesn’t have to use the same element labels (names) for similar content, or allow the same terms to be filled in to each element as another standard (the target standard).

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