// Papers on Joelle (ownership for active objects)

Joelle: Minimal Ownership for Active Objects

Dave Clarke, Tobias Wrigstad, Johan Östlund & Einar Broch-Johnsen.

Appeared at the Sixth ASIAN Symposium on Programming Languages and Systems (APLAS), Bangalore, India, December 2008.


Active objects offer a structured approach to concurrency, encapsulating both unshared state and a thread of control. For efficient data transfer, data should be passed by reference whenever possible, but this introduces aliasing and undermines the validity of the active objects. This paper proposes a minimal variant of ownership types that preserves the required race freedom invariant yet enables data transfer by reference between active objects (that is, without copying) in many cases, and a cheap clone operation where copying is necessary. Our approach is general and should be adaptable to several existing active object systems.

Download paper     Extended tech-report (recommended)

Extended Tech-Report

A much extended description of the Joelle work, most notably including a formal semantics of the concurrent and ownership systems is available here. It is recommended reading over the above paper, which had to cut those bits out due to the severe (16 pages LNCS) page restrictions at APLAS.