Abstract: Methods, systems, and apparatus are described for managing metadata for a distributed processing system. In one aspect, a method includes receiving a computation specification that includes a set of grains that specifies an initial state for a computation that is to be performed by a distributed processing system, wherein each grain comprises metadata that specifies a portion of the initial state for the computation; storing a grain hierarchy that represents a state for the computation based on a grain type associated with each grain, the grain hierarchy comprising subscription grains for subscriptions for the grain hierarchy, each subscription corresponding to one or more grains included in the grain hierarchy, and each subscription specifying one or more actions to be performed by the hub device; and performing, during performance of the computation, at least one of the actions specified by at least one of the subscriptions.

Abstract: A system for software development provides an underlying object-oriented programming language and a language front-end supporting software development in a programming methodology of the object-oriented programming language, the system providing a graphical programming environment permitting access to classes of the object-oriented programming language and permitting subclasses to be defined and modified dynamically (“dynamic classes”) while the software under development is executing. Modifications to the dynamic classes can be reflected in future instances of the classes and in instances of the classes existing prior to the changes. In one embodiment, the object-oriented programming language is Java. The dynamic classes coexist with compiled classes of the object-oriented programming language, the dynamic and compiled classes each being capable of calling methods on instances of any class.

Abstract: A system and method for hypervideo object tracking in a compressed digital video environment includes a hypervideo authoring system and a hypervideo browser. The hypervideo authoring system permits one or more moving objects in an MPEG compressed video clip to be identified, tracked, refined, edited, and associated with a specified action with a minimum of user intervention. The hypervideo browser allows the MPEG video to be viewed and objects of interest to be selected by a user, thereby hyperlinking to additional information of interest.