Abstract. This paper describes the motivations for and main features of Tigger { a framework for the construction of a family of object-support operating systems that can be tailored for use in a variety of di erent application domains. An important goal of the design of Tigger is that instantiations of the framework should be able to support (a number of) di erent object models in order to allow a range of object-oriented languages for distributed or persistent programming to be supported without unnecessary duplication of e ort. A further goal of the design is that instantiations of the framework should be able to support the same object model in di erent w ays depending on the requirements of the applications to be supported by t h o s e i n s t a n tiations. This paper describes the main features of the Tigger framework that allow t h e s e goals to be realised.