Elvin is an event routing service using a publish/subscribe event delivery model. It was developed at the Distributed Systems Technology Centre, an Australian co-operative research centre at the

University of Queensland The University of Queensland is a Public university, public research university located primarily in Brisbane, the capital city of the Australian state of Queensland. Founded in 1909 by the Queensland parliament, UQ is one of the six sandstone ...

that operated from 1992 until mid-2006.

The Elvin publish subscribe model

Elvin is most distinguished from other such systems by its support of a sophisticated content-based subscription system. Elvin clients subscribe to events using a language that resembles C boolean expressions. For example:

  Department  "IT" && Percent-Disk-Free <= 10

This expression selects messages that have a field named Department with a string value matching "IT" and a Percent-Disk-Free field with an integer value less than or equal to 10. The Elvin subscription language supports a range of operations for matching numeric and string values, including the use of

regular expression A regular expression (shortened as regex or regexp), sometimes referred to as rational expression, is a sequence of characters that specifies a match pattern in text. Usually such patterns are used by string-searching algorithms for "find" ...

matching. Elvin is oriented around providing a fast, flexible event service that can be federated to form wide-area event notification networks. In order to achieve these goals it does not provide persistence,

durability Durability is the ability of a physical product to remain functional, without requiring excessive maintenance or repair, when faced with the challenges of normal operation over its design lifetime. There are several measures of durability in us ...

or guaranteed delivery.Although Elvin does not provide hard delivery guarantees, the use of TCP as the usual underlying transport provides some guarantees at the communications layer, and the protocol has mechanisms that allow clients to be notified in the rare event that a message cannot be delivered. Elvin can thought of as providing a middle ground between low-level network multicast and higher-level, more complex, event brokers such as JMS.

Commercialization

In 2003, the research group that created Elvin left DSTC to found Mantara software in order to develop commercial applications of Elvin. In November 2006, Mantara announced that it would be ceasing to support Elvin as a standalone commercial product by the end of 2007. The specifications for the Elvin protocols have been made available, and a new implementation of Elvin has subsequently been developed, Avis, an open-source ( GPL) implementation.

Notes

References

{{Reflist

External links

* Th
elvin.org
web site.

1997, Bill Segall and David Arnold, Proceedings AUUG97, Brisbane Australia, September 1997.
Content Based Routing with Elvin4
2000, Bill Segall, David Arnold, Julian Boot, Michael Henderson and Ted Phelps Proceedings AUUG2k, Canberra, Australia, June 2000.
Avis
Message-oriented middleware