The Yahoo Geocode meta cartridge searches for vCard addresses or iCalendar locations in the source graph and looks up the latitude or longitude of the address or location using a Yahoo geocoding service.
Yahoo's Geo offerings include the paid for BOSS PlaceFinder service. However, it is also possible to access the PlaceFinder data through YQL. Access via this mechanism is at the individual discretion of the user - use of the YQL table geo.placefinder is free subject to non-commercial use.
The meta cartridge uses the public YQL endpoint, http://query.yahooapis.com/v1/public/yql, for which no API key is required. The YQL table for PlaceFinder is rate limited to 2000 queries per day.
When searching for RDF vCard addresses in the source data, the cartridge omits any already containing geo:lat and geo:long entries (depending on the extractor cartridge(s) used to produce the source Linked Data, these coordinates may already have been supplied). Only the postal code and country fields in the vCard are used for PlaceFinder searches. Both must be present - a post code alone is not sufficiently unambiguous. e.g. 74170 is valid in both the U.S. and France. The geo:placefinder table data does not include street addresses; so these aren't used for searches, nor is the city field. The combination of post code + country is considered more specific.
Many extractor cartridges create vCard addresses (vCard:ADR objects) attached to iCalendar location fields. The meta cartridge looks for iCalendar locations in the source graph and geocodes any associated vCard address as described above.