The process of metadata mappings in CARARE supports subsequent critical activities:
Metadata, literally “data about data”, provide a wide variety of information describing a resource, such as the subject matter and its creators, technical information to store and access the resource, legal rights, etc. Metadata records are critical to the documentation and maintenance of interrelationships between information resources and are being used to find, gather, and maintain resources over long periods of time. The consistent application of a descriptive metadata standard improves the user's search experience and makes information retrieval within a single collection or across multiple collections more reliable. Administrative, technical, and preservation metadata contribute to the management of information resources and help to ensure their intellectual integrity both now and in the future.
In parallel with other domains, many researchers in the digital cultural heritage community recognize the need to lower the barriers for the management and aggregation of digital resources, by implementing some measure of interoperability among metadata standards and then with proprietary data structures. There is a wide range of proposed solutions, including crosswalks, translation algorithms, metadata registries, and specialized data dictionaries. One definition of interoperability is “the ability of different types of computers, networks, operating systems, and applications to work together effectively, without prior communication, in order to exchange information in a useful and meaningful manner. Interoperability can be seen as having three aspects: semantic, structural and syntactic. Semantic mapping is the process of analyzing the definitions of the elements or fields to determine whether they have the same or similar meanings. Structural interoperability refers to the presence of data models or wrappers that specify the semantic schema being used. Syntactic interoperability, also called technical interoperability, refers to the ability to communicate, transport, store, and represent metadata and other types of information between and among different systems and schemas.
A crosswalk provides a mapping of metadata elements from one metadata standard to another. The prerequisite to a meaningful mapping requires a clear and precise definition of the elements in each standard. The primary difficulty is to identify the common elements in different metadata schemas and put this information to use in systems that resolve differences between incompatible records. Crosswalks are typically presented as tables of equivalent elements in two standards and, even though the equivalences may be inexact, they represent an expert's judgment that the conceptual differences are immaterial to the successful operation of a software process that involves records encoded in the two standards. A crosswalk supports the ability of a retrieval mechanism to query fields with the same or similar content in different data sources; in other words, it supports semantic interoperability. Crosswalks are not only important for supporting the demand for single point of access or cross-domain searching; they are also instrumental for converting data from one format to another. However, aggregating metadata records from different repositories may create confusing display results, especially if some of the metadata are automatically generated or created without following best practices or using standard thesauri and controlled vocabularies. Mapping metadata elements from different schemas is only one level of crosswalking. At another level of semantic interoperability are the data content standards for formulating the data values that populate the metadata elements, for example, rules for recording personal names or encoding standards for dates.