One of the central aspects in an Information System is the meaning of data in the external world and the information carried by them. We propose a Constructive Object Oriented Modeling Language (COOML) for information systems, based on a constructive logic of pieces of information. The focus is on the definition of a data model suitable for organizing the information stored in OO sytems. The underlying constructive logic supports a correct way of storing, exchanging and elaborating information.