In many of the previous chapters, we have discussed the fact that social graphs comprise two elements: relationships to people (your human social graph) and relationships to things (your entity social graph). The Open Graph protocol focuses on the latter, building web pages to become rich information entities in our social graph.
Entity relationships are vitally important in defining who a user is and what her interests are and help us determine, for example, products that she may be more inclined to purchase or other things she may be interested in. Entity relationships can help us target everything from applications to ads directly to the user’s social profile—that is, to who she is on the Web. The more information that is available in a user graph, the more relevant our targeting can be for that user.
Let’s explore how the Open Graph protocol works to define user entities, learn how to implement the metadata behind the protocol, and view some practical examples of the protocol being used in the wild.