Live distributed object

Definition

An illustration of the basic concepts involved in the definition of a live distributed object.

The term live distributed object (also abbreviated as live object) refers to a running instance of a distributed multi-party (or peer-to-peer) protocol, viewed from the object-oriented perspective, as an entity that has a distinct identity, and encapsulates state and behavior.

The identity of a live distributed object is determined by the same factors that differentiate between instances of the same distributed protocol: the object consists of a group of software components running on some set of physical machines and engaged in mutual communication, each executing the distributed protocol code with the same set of essential parameters, such as the name of a multicast group, the identifier of a publish-subscribe topic, the identity of a membership service, etc. The components are referred to as live distributed object's proxies.

The state of a live distributed object is defined as the sum of all internal, local states of its proxies. By definition, it is distributed and replicated. The different replicas of the object's state may be strongly or only weakly consistent, depending on the protocol semantics: an instance of a consensus protocol will have the state of its replicas strongly consistent, whereas an instance of a leader election protocol will have a weakly consistent state.

The behavior of a live distributed object is characterized by the set of possible patterns of events (messages) that may be sent to or received from its proxies.

References

• Ostrowski, K., Birman, K., and Dolev, D. (2007). "Live Distributed Objects: Enabling the Active Web", IEEE Internet Computing, November-December 2007, 11(6):72-78, http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?isnumber=4376216&arnumber=4376231.
• Ostrowski, K., Birman, K., Dolev, D., and Ahnn, J. (2008). "Programming with Live Distributed Objects", Proceedings of the 22nd European Conference on Object-Oriented Programming, Paphos, Cyprus, July 07 - 11, 2008, J. Vitek, Ed., Lecture Notes In Computer Science, vol. 5142, Springer-Verlag, Berlin, Heidelberg, 463-489, http://portal.acm.org/citation.cfm?id=1428508.1428536.
• Ostrowski, K. (2008). "Live Distributed Objects", Ph.D. Dissertation, Cornell University, http://hdl.handle.net/1813/10881.
• Ahnn, J., Birman, K., Ostrowski, K., and van Renesse, R. (2008). "Using live distributed objects for office automation", Proceedings of the ACM/IFIP/USENIX Middleware '08 Conference Companion, Leuven, Belgium, December 01 - 05, 2008, Companion '08, ACM, New York, NY, 30-35, http://portal.acm.org/citation.cfm?id=1462735.1462743.