Abstract: A method and apparatus for assisting in the optimization of a complex, hierarchical data structure, such as a process flow model, comprising a plurality of elements such as tasks to be carried out, each element having data dependency upon other elements within the hierarchy. The apparatus includes a database for maintaining a data set incorporating a plurality of dependency structure matrices, each dependency structure matrix corresponding to one hierarchical level in the data set; display means for displaying, to the user, a representation of said dependency structure matrices; user input means for effecting the change of a data dependency of a selected element at a selected level in said hierarchy; and data manipulation means for effecting consequential changes in the data set representing said changes in dependency of elements throughout the hierarchical structure.

Abstract: Acoustic devices, attached to fishing nets, reduce or avoid by-catch of marine animals during fishing operations. The acoustic devices emit a deterrent signal to a particular marine animal on actuation by the approach of the animal. At least one of the devices is an active device that detects marine animal emitted stimuli and responds with a suitable response emission.