Effective Synchronisation of Concurrent Objects: Laying the Inheritance Anomaly to Rest

The integration of concurrency and object-oriented programming has been a goal of researchers for over a decade. To date, attempts to address reuse conflicts, known as “inheritance anomalies”, have been limited in applicability and have not addressed all the issues that synchronisation raises. In this paper we take a detailed look at synchronisation by investigating five different aspects which must be considered. We investigate the different forms of the inheritance anomaly which can arise and look at how they can be avoided, either through the use of specific features of concurrent object-oriented languages, or common techniques of object-oriented programming. Finally we present a set of requirements for a concurrent object-oriented language to support a flexible concurrency model with an emphasis on the reuse of both synchronisation and functional code.