Formal Description Of The Technical Lotos And Its Extensions And Applications In Real-time Systems

The formal description technique (FDT) is an important tool for the design, analysis and specification of an information processing system (IPS). We can get a complete, consistent, concise, unambiguous and precise specification of a system with FDTs. Nowadays FTDs have been studied further and standardized at the international level such as SDL, ESTELLE and LOTOS.LOTOS (language of temporal ordering specification) is a language that fits the requirement of protocol engineering, distributed processing and parallel processing. It consists of two parts: The first is based on process algebra, concerning the description of process behavior and interaction, the other is built on the foundation of formal representation theories for abstract data type(ADT), meaning the description of data structure and value representation.Standard FDT lacks the capabilities of expressing time-related behaviors, however many application areas require much attention to the time, like manufacturing, avionics and multimedia systems. Particularly, along with the continuous development of service and protocol for multimedia, the time control has become (he nucleus and main fraction of a new service QoS requirement The traditional FDT LOTOS can't satisfy the describing requirementAccording to the shortage of the traditional LOTOS, we have added some extra timed operations, made some real-time expansions to the LOTOS operational semantics, and proposed several LOTOS real-time extensions like TLOTOS, ET-LOTOS, RT-LOTOS and E-LOTOS. E-LOTOS is the latest version of enhancements of LOTOS, which is published by ISO in 1998. It supports the viewpoint of quantitative time, improves the method of definition of the data type and the value structure of predefine types, it has a good modularity, and the definition of the generic modules is very useful for the code reuse.Finally, in order to access the extensions of LOTOS, we offer a distributed multimedia system, give the system structure of it based on the formal technique E-LOTOS, and described it completely with E-LOTOS.