We're working on this problem at Datafiniti (https://www.datafiniti.net https://www.datafiniti.net). Since we index hundreds of sources for a similar service,

We're working on this problem at Datafiniti (https://www.datafiniti.net https://www.datafiniti.net). Since we index hundreds of sources for a similar service, we can leverage some basic string comparison techniques to normalize records from different sources and fill in attributes that are missing from any one source.