This paper presents a new conceptual framework for summarization that considers the relationship between entities, device properties and user information needs. We summarize using a skim — an audio-visual clip that is a drastically condensed version of the original video. An entity is defined to be a sequence of elements that are related to each other by a certain property. In this paper we discuss the causes, the different entity types and also present a skim taxonomy. Each entity is associated with a utility. The skim is generated by a constrained utility maximization over those entity-utilities that satisfy the user information needs as well as the device rendering capabilities. We construct an optimal skim within this framework that retains a particular subset of entities. These entities have been chosen since they can be automatically computed in a robust manner. The user studies show that the optimal skims perform well in a statistically significant sense, at compression rates...