Abstract: A user interaction data storage system stores user interaction data received from online systems as records. Each record of user interaction data describes user interactions performed by a user with an online system. A system, for example, a content provider system performs data access requests to access user interaction data so as to determine whether a user is likely to be interested in a content item. A plurality of online systems store a block chain comprising blocks that records transactions. Some transactions of the block chain are associated with data contribution operations and some transactions of the block chain are associated with data consumption operations.

Abstract: A digital magazine server receives content items from various sources or information identifying content items maintained by various sources. Based on characteristics of the content items, the digital magazine server identifies themes of various content items. A theme of a content item identifies a primary topic or primary meaning of the content item. In various embodiments, the digital magazine server determines the theme of a content item based on words within the content item, accounting for meanings of words in the content item, parts of speech of each word, combinations of words in the content item, and syntax of words in the content item.

Abstract: A user interaction data storage system stores user interaction data received from online systems as records. Each record of user interaction data describes user interactions performed by a user with an online system. A system, for example, a content provider system performs data access requests to access user interaction data so as to determine whether a user is likely to be interested in a content item. A plurality of online systems store a block chain comprising blocks that records transactions. Some transactions of the block chain are associated with data contribution operations and some transactions of the block chain are associated with data consumption operations.