Google has a very nice demonstration of web application that extracts information from Freebase and displays it on a Google map. It uses the Google Maps JavaScript API and the Freebase knowledge base to find entities and facts associated with places on a map. The source code is available on Github and is just a small amount of javascript and some css (via less) files.

“The app uses browser’s geolocation feature to find user’s location and displays a map of interesting objects that can be found nearby (within 50 000 ft). It uses the Freebase Search API to find relevant objects. When user clicks on one of the markers, the app calls the Freebase Topic API to fetch more information about that object. Once the information is retrieved, it populates a purejs template to display a knowledge card for the user.”

This sort of application has been done many times before with RDF and the Google approach can be adapted to query an arbitrary RDF resource for custom knowledge bases.