Schema Crosswalk

Schema Crosswalk

A crosswalk is a table that shows equivalent elements (or "fields") in more than one database schema. It maps the elements in one schema to the equivalent elements in another schema.

Crosswalk tables are often employed within or in parallel to enterprise systems, especially when multiple systems are interfaced or when the system includes legacy system data. In the context of Interfaces, they function as a sort of internal ETL mechanism.

For example, this is a metadata crosswalk from MARC to Dublin Core:

Crosswalks show people where to put the data from one scheme into a different scheme. They are often used by libraries, archives, museums, and other cultural institutions to translate data to or from MARC, Dublin Core, TEI, and other metadata schemes. For example, say an archive has a MARC record in their catalog describing a manuscript. If the archive makes a digital copy of that manuscript and wants to display it on the web along with the information from the catalog, it will have to translate the data from the MARC catalog record into a different format such as MODS that is viewable in a webpage. Because MARC has different fields than MODS, decisions must be made about where to put the data into MODS. This type of "translating" from one format to another is often called "metadata mapping" or "field mapping," and is related to "data mapping," and "semantic mapping."

Crosswalks also have several technical capabilities. They help databases using different metadata schemes to share information. They help metadata harvesters create union catalogs. They enable search engines to search multiple databases simultaneously with a single query.