Using LOTOS in the specification of industrial bus communication protocols
The aim of this paper is to expose the utility of formal description techniques (FDTs) applied to the design of industrial communication protocols (fieldbuses). For this purpose the authors explain their experience in the formal specification of the data link layer of the WorldFIP French standard. 
 
Nowadays there is in the market a great number of protocols in the framework of industrial communications. They are devised for specific applications and distributed control processes. Every manufacturer has tied its customers to its own proprietary fieldbuses, which has led this technology to a great lack of standardization. Thus, the interconnection of equipment from different manufacturers has become very problematic. In this paper an introduction to fieldbuses is given, with an explanation of their main features, standardization attempts and applications. 
 
WorldFIP is a fieldbus network protocol designed to provide links between sensors/actuators and process units (PLCs, controllers, etc.) in automation systems. This protocol has been proposed by French manufacturers and has become a standard. This paper analyses the data link layer of WorldFIP, specifying it with the formal language LOTOS. This is a formal description technique (FDT) standardized by ISO (International Organization, for Standardization) for designing services and protocols used in the communication of open systems (OSI: Open systems Interconnection). Also, the methodology followed for validating the formal description is explained. Finally an executable that constitutes a simulation system for WorldFIP networks is implemented following this specification.