||Supporting data sharing among different disciplines, applications, and users in the building industry is a complex and difficult task. Standardization efforts and research into product models have since long attempted to facilitate data exchange among building partners, with little result so far. Different technologies have resulted in different approaches, in particular, an object-oriented approach has led to the specification of IFCs as a basis for information sharing, while other initiatives adopt XML as a flexible language for marking up and describing project information. We propose a concept for representational flexibility, named sorts, that combines many of the advantages of both approaches. Based on an extensible vocabulary of representational classes and compositional relationships and grounded in an object-oriented framework that has each of the representational classes specify its own operational behavior, it will enable a designer to define, develop, and adopt alternative design representations that can suit a specific purpose or task at hand.