Consider a typical source on data modeling: it is a thick book, with lots of pictures, and not too many concepts. It usually presents a new modeling method and sells a CASE tool. Sometimes it may be used as a cookbook. After reading it you will not have learned any new concepts, but you will be able to create hundreds of neat pictures destined to become shelfware. If the world you are modeling does not fit into the method or tools, the best you can do is to use English comments. This paper is thin and has almost no pictures. It does not introduce new methods and does not try to sell a CASE tool, neither is it a cookbook. It presents information modeling concepts based on simple ideas drawn from programming in general and object- oriented programming in particular. These concepts have been widely used for understanding, creating, and reconciling informa- tion models within Bellcore.