This paper introduces notions of weak robust observability, lull information weak robust controllability, and partial information weak robust controllability for a class of uncertain linear systems in which the uncertainty satisfies an integral quadratic constraint. The paper gives characterizations of these properties in terms of the existence of suitable solutions to Riccati differential equations of the type which occur in H-infinity control. Furthermore, it is shown that the conditions of weak robust observability and full information weak robust controllability are necessary but not sufficient for partial information weak robust controllability.