1. A computer-implemented method for determining user interests, comprising: receiving user activity data that describes an interaction between a user and digital content; generating first interest-level data that represents a first level of interest between said user and a first entity and a second entity that are a topic of said digital content, wherein said first entity and said second entity are included within a knowledge base comprising a plurality of entities, said knowledge base comprising an ontology comprising a knowledge graph that indicates relationships between said plurality of entities; identifying a candidate entity based on said candidate entity having a relationship to both the first entity and the second entity within the knowledge base; generating second interest-level data that represents a second level of interest between said user and said candidate entity based on an analysis of said relationships between the candidate entry and the first entity and the second entity; linking a user ID associated with the user to the candidate entity, thereby indicating the user is interested in the candidate entity; receiving a search query from the user; and generating a search result comprising digital contents, in response to the received search query, wherein the digital contents are ranked using the generated first interest-level data and the generated second interest-level data.