External Uniqueness Is Unique Enough

  • Dave Clarke
  • Tobias Wrigstad
Conference paper

DOI: 10.1007/978-3-540-45070-2_9

Part of the Lecture Notes in Computer Science book series (LNCS, volume 2743)
Cite this paper as:
Clarke D., Wrigstad T. (2003) External Uniqueness Is Unique Enough. In: Cardelli L. (eds) ECOOP 2003 – Object-Oriented Programming. ECOOP 2003. Lecture Notes in Computer Science, vol 2743. Springer, Berlin, Heidelberg


External uniqueness is a surprising new way to add unique references to an OOPL. The idea is that an externally unique reference is the only reference into an aggregate from outside the aggregate. Internal references which do not escape the boundary of the aggregate are innocuous and therefore permitted. Based on ownership types, our proposal not only overcomes an abstraction problem from which existing uniqueness proposals suffer, it also enables many examples which are inherently not unique, such as a unique reference to a set of links in a doubly-linked list, without losing the benefits of uniqueness.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2003

Authors and Affiliations

  • Dave Clarke
    • 1
  • Tobias Wrigstad
    • 2
  1. 1.Institute of Information and Computing SciencesUtrecht UniversityUtrechtThe Netherlands
  2. 2.Department of Computer and Systems SciencesStockholm University/KTHStockholmSweden

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