A monitoring based approach to object oriented real time computing

1 Introduction Future real-time applications will become large and physically distributed among different sites. They will have to work in environments that are so complex that it is not possible to specify all possible states and conditions in detail. At the same time, the time-to-market from the first idea to the working product decreases , especially as real-time technology is no longer restricted to long-living embedded applications, like in aircrafts or defense systems, but also penetrates business and customer applications. Many of today's Internet-applications have an increasing demand for real-time behavior. This starts from hard real-time telemetric-applications and critical trading applications, like stock trading, includes all kinds of multimedia-applications and ranges to multi-player games. An important issue, that all these applications have in common, is that they do not act in a closed environment. They act in environments that are usually not controlled by a single principal, like one company that runs an application-server or one telecom carrier that manages the whole network. Large scale distributed real-time applications (e.g. over the Internet) usually have to use resources from different entities. This immediately leads to a need for agreed common interfaces , i.e. standards that allow for interaction in a heterogeneous environment. Open standards have driven the expansion of the Internet and today it is commonly agreed that only applications that use and provide standard interfaces have the potential to become successful. Today, even closed applications (e.g. on the Intranet) are usually designed and implemented using these standards. However, these standards mainly have focused on functional behavior. Specification of timing behavior was initially out of scope. This is true for the major Internet protocol standards, like e.g. TCP/IP, IEEE 802.x, or HTML, as well as for commonly used interface description languages like CORBA or DCOM IDL. Also all common implementation languages (ranging from C/C++, Java to SQL) do not provide means to express timing behavior. What is needed are open standards that include timing and cope with the heterogeneity. The benefits of object-orientation in system development and for handling het-erogeneity are well accepted from the software engineering point of view. Today nearly all new IT systems emerge from an object-oriented analysis and modeling phase, their implementations are based on object-oriented middleware (like DCOM or CORBA), they are written in an object-oriented language (like C++ or Java), and their APIs are offered in abstractions of classes and objects. The desired properties of …