redefinitions. Ideally, this should not be necessary. Several concurrent object-oriented languages [31,22,38] have been introduced to solve the synchronization constraint inheritance anomaly problem, although most of these languages (still) suffer from this problem in one way or another.
Recently, there have been some attempts in defining real-time object-oriented languages [52,17,32,27,44]. These languages aim at reducing the complexity of applications through modularization so that predictability and reliability of applications can be increased. In addition, the inheritance mechanism can be useful in reusing welldefined and verified real-time programs. Similar to concurrent object-oriented languages, real-time object-oriented languages may suffer from the real-time constraints inheritance anomaly. In contrast to concurrent object-oriented languages, however, there has been almost no study on the origins of the real-time constraint inheritance anomaly problem. Needless to say, the combined analysis of concurrent and real-time constraint inheritance anomalies has not been addressed, although most real-time systems are concurrent.
It is important to note that both the synchronization and real-time constraint inheritance anomalies are not inherent in combining synchronization and real-time specifications with inheritance. On the contrary, the anomalies are largely language-dependent. How a language implements synchronization and real-time constraints and inheritance can be the major cause of inheritance anomalies.
This paper has two contributions. First, it presents generic object-oriented synchronization and real-time models which are useful in analyzing and relating synchronization and real-time constraint inheritance anomalies in a uniform way. These generic models help in searching for solutions that can deal with both problems. Based on these generic models, a number of important synchronization and real-time inheritance anomalies are identified and discussed.
Second, as a possible solution to both synchronization and real-time constraint inheritance anomalies, this paper proposes modular and composable synchronization and real-time specification extensions to the object-oriented model using the concept of composition-filters. Composition-filters can affect the synchronization and real-time characteristics of the received and sent messages. By proper configuration of the filters, one can specify synchronization and real-time constraints, as well as reuse of these