Information processing is often such a large and complex artifact that it goes beyond a human being's capacity to conceive, model and develop it with all of its aspects at a time. For this reason, it is typical for one to focus on some aspects of it in one time and on other aspects in another time, depending on the problem at hand. For recurrent situations it is necessary to have a structured and well-defined set of perspectives which guide selections and shifts of focuses. This paper presents a light-weight perspective ontology which provides a set of well-defined perspectives, established on three dimensions, to conceive issues in information processing in an organized manner. The perspective ontology can be applied on different information processing layers, such as information systems (IS), information systems development (ISD) and method engineering (ME). To demonstrate the applicability of the ontology, it is used to derive a set of IS perspectives with basic IS concepts and constructs. The IS perspectives are then deployed as a framework in a comparative analysis of current perspectives in the IS literature.