Last week at Where 2.0, Yahoo's Gary Gale discussed "geosetta", the concept of a geographic Rosetta Stone, which allows for a unified conversion of geographic namespaces based on different geographic reference identifiers (e.g., Yahoo's Where on Earth ID, or WOEID). The idea behind geosetta is that developers should be able to easily identify and cross reference a location among multiple service providers despite any disparities that may be inherent in the respective namespaces.
As part of its GeoPlanet API, Yahoo has introduced concordance, which is a new feature that allows for access to a unified object that cross references several other namespaces, including WOEIDs, ISO 3166, FIPS, INSEE, Geonames, JGDC, IATA and ICAO. You can take a look at the updated documentation for GeoPlanet to get a sense of what concordance offers.
Gary Gale sums up concordance on the Yahoo Geo Technologies Blog:
So what is concordance? We use this word to talk about how a place is identified by those disparate building blocks. We all have our unique identifiers, ours are WOEIDs, which allow placed to be catalogued and identified; we call these namespaces. We’ve collected these identifiers and namespaces as a single object, a concordance, which empowers a user to reference each source. You can think of it as a mapping of an identifier in a namespace to its equivalent in another namespace. But it’s not a joining of information; we’re only enumerating the identifiers, not the back-end data or attributes that they describe.
While GeoPlanet's concordance does yet cross reference with all other geographic namespaces out there, the new feature is a great step for developers working with mashups that link up multiple data sets. And we look forward to seeing how concordance is integrated with new and existing mashups that offer geolocation and mapping functionality.