This topic covers the basic elements of Freebase and examines a topic to illustrate how they work together.
The Basic Data Components: Commons, Bases, Types, Properties, and Topics
There are four basic elements that make up Freebase content. Moving from the most general level to the most specific, they are:
- Bases and Commons
- Types
- Properties
- Topics
Bases are collections of topics created by users. Commons are similar to bases in that they also gather topics together under a common category, but in this case the categories are very general. If you're building a base, the Commons can provide a starting point for finding and collecting topics. In technical database terms both bases and commons would be called domains, and you'll sometimes see this term used in our documentation for application developers.
Types identify a topic as being an example of a particular type of thing, along with specific information about it. For example, the Film commons contains types such as Film Actor, Film Festival, Film Distributor, Film Rating, and Film Format, among many others. Users can also create their own types and add them to topics. The most important concept behind types is that new or existing types can be added to a topic in order to provide additional information about it and to add it to a base.
Properties are the specific information elements within a type. For example, the Film Actor type has three properties: Film Performances, Film Dubbing Performances, and IMDb Entry. When the Film Actor type is added to a topic, the properties are the fields of information that a user fills out for that specific topic.
Topics are specific examples of a type. Adding a type to a topic is a way of saying "This topic is an example of the _____ type." The most important concept behind topics is that instead of being stand-alone containers of information as they would be in a conventional database, Freebase topics are information hubs that can be linked to other bases (and topics) by adding new types to them.
Anatomy of a Topic
By looking at an example topic you can see how all the elements of base, commons, type, and properties come together. Let's look at Arnold Schwarzenegger, who has had a multi-faceted life that is reflected in his multi-faceted topic.
We can see that Arnold can be found in five Commons categories: People, Film, Government, Sports, and Awards. In addition, he can be found in the user-created base American Comedy. We can also see that under the Film commons he is associated with two types, Film Actor and Film Producer, where in the other commons categories he is only associated with one type each (though when he dies, we can expect that the Deceased Person type will be added to his topic in the Person category).
Looking at the Film Actor type for Arnold we can see that users have filled in the names of his films for the Film Performances property. If you click the 1 Empty Field link you will see that the property Film Dubbing Performances is currently empty; if Arnold should ever have film dubbing performance, a user could click Edit for that property and enter the name of the film. (Note that the IMDb Entry property appears as a Web Link on the right side of the page, rather than under the Film Actor type).
The most interesting aspect of Arnold's topic is that it includes a user-created type, Impersonated Celebrity, from the American Comedy base. This illustrates the concept of topics as information hubs, or nodes, that can be linked into a multitude of other commons categories, bases, and topics (in this case, Rich Little and Phil Hartman) through the mechanism of the type. It also shows how users can create their own mechanisms for categorizing new and existing topics and subsequently expand the range of information available to all users.
