Information logistics aims at demand-oriented just-in-time information supply to individuals and organisation units in enterprises. This paper contributes to research in information logistics by investigating dimensions of information demand and by defining an approach to information demand modeling. Our approach primarily consists of the concept of a "context" consisting of processes, organisation structure, resources and contact network. Furthermore, we integrate our apporach with the earlier developed notion of situation. In order to validate applicability of our approach, we investigate the field of collaborative engineering. An example context and typical situations in collaborative engineering are presented.