Moving Between Standards (Crosswalking)

Crosswalks are documents that map metadata elements between different metadata standards. The crosswalk may be presented as a document for humans to read, in which case the crosswalking process must be performed by humans who are referencing the document. Alternatively, a crosswalk document may be expressed in such a way that a computer can automatically perform a mapping from one metadata standard to another.

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 simultaneously change the format and fields (i.e., the content standard) and the values within those fields (i.e., the vocabulary) to meet the requirements of the second standard.

Due to the complexity of metadata content standards, there are few automated processes to translate between content standards. Even in those cases where translations exist, inevitably some information is lost when translations are made. This is due to the complexity of the standards and potentially non-overlapping subject areas that the standards apply to. In this case, even manual translation between standards does not result in complete information transfer.

The Crosswalking Process

The process of mapping between content standards or vocabularies is usually divided into the following steps: harmonization, semantic mappings, rules, and transformation. Each of these is described in a separate guide linked below.

In these descriptions, the term 'schema' means a set of rules that define how something is represented.