Integrating object-oriented programming and protected objects in Ada 95

Integrating concurrent and object-oriented programming has been an active r esearch topic since the late 1980's. There is now it plethora of methods fo r achieving this integration. The majority of approaches have taken a seque ntial object-oriented language and made it concurrent. A few approaches hav e taken a concurrent language and merle it object-oriented. The most import ant of this latter class is the Ada 95 language, which is an extension to t he object-based concurrent programming language Ada 83. Arguably, Ads, 95 d oes not fully integrate its models of concurrency and object-oriented progr amming. For example, neither tasks nor protected objects are extensible. Th is article discusses ways in which protected objects can be made more exten sible.