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Existential Owners for Ownership Types

Tobias Wrigstad, Stockholm University/Royal Institute of Technology, Sweden
Dave Clarke, CWI, The Netherlands


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This paper describes a lightweight approach to adding run-time checked downcasts to a language in the presence of ownership types without the need for a run-time representation of owners. Previous systems [6] have required owners of objects to be tracked and matched at run-time which is costly in terms of memory and performance. Our proposal avoids run-time overhead to deal with owners and also extends the expressiveness of ownership-based systems enough to handle the Java equals idiom for structural equality comparison. The price is that it is sometimes impossible to downcast a type into a type that can be statically aliased. Our proposal is completely orthogonal and combinable with previous work.

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About the authors

Tobias Wrigstad is a lecturer at the department for computer and systems sciences, Stockholm University/Royal Institute of Technology, Kista. His main areas of interest are object-oriented programming, formal methods and dynamic programming languages. He can be reached at Also see tobias.

Dave Clarke is a postdoctoral researcher in the SEN3 "Coordination Languages and Models" Group at CWI in The Netherlands. His main areas of interest are coordination languages, object- and aspect-oriented programming, game theory and formal methods. He can be reached at Also see dave/

Cite this article as follows:Tobias Wrigstad and Dave Clarke: "Existential Owners for Ownership Types", in Journal of Object Technology, vol. 6, no. 4, May-June 2007, pp. 141-159


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