Abstract: Techniques and/or systems are provided for performing an action based upon a subscription to multi-source data. That is, a subscription may specify one or more actions that are to be performed upon satisfaction of a set of conditions associated with one or more data sources. For example, a subscription for a user Joe may specify that a flower order is to be placed when a current date is Valentine's day, a social network profile for Joe indicates Joe has a significant other, and a local flower shop has roses in stock. In this way, a subscription may be based upon various data sources, such as a calendar, a social network, and a flower supply data source. Because a vast number of subscriptions may be maintained, conditions may be organized into a graph such that a condition, shared by multiple subscriptions, is represented by a single node within the graph.