1. A method implemented in a data processing apparatus, comprising: obtaining, by a template engine of a notification system that includes the template engine, a notification generator, and a template database that stores multiple templates that each define (i) respective trigger criteria for presenting a respective notification and (ii) respective content rules for determining respective content to include in the respective notification, a template that defines (i) trigger criteria for presenting a notification and (ii) content rules for determining content to include in the notification, from the template database; accessing, by the template engine, enterprise resources of an enterprise, the enterprise resources including data describing entities related to the enterprise and relationships among the entities and a transcription of an ongoing meeting; accessing, by the template engine, user information specific to a user, the user information including information not described by the enterprise resources that are accessible to the user; determining, by the template engine, that the trigger criteria defined by the template is satisfied by the enterprise resources and the user information based at least on a determination that the enterprise resources describe that the user is currently in the ongoing meeting and the user information includes a personal document that is relevant to a next topic of the ongoing meeting according to the transcription of the ongoing meeting; in response to determining that the trigger criteria defined by the template obtained from the template database is satisfied by the enterprise resources and the user information based at least on the determination that the enterprise resources describe that the user is currently in the ongoing meeting and the user information includes the personal document that is relevant to the next topic of the ongoing meeting according to the transcription of the ongoing meeting, generating, by the notification generator, a particular notification that identifies the personal document that is relevant to the next topic of the ongoing meeting based at least on the content rules defined by the template obtained from the template database; and in response to generating the particular notification, providing the particular notification to a computing device of the user for display to the user.