The safety-bag expert system in the electronic railway interlocking system elektra

Abstract

Abstract The real-time expert system “Safety-Bag” is an integral part of the electronic railway interlocking system ELEKTRA. The interlockinh system contains a logic channel, which processes commands, and a safety channel, which checks the commands according to safety rules. Commands which are only allowed under certain circumstances are carried out only if the instructions generated by processing the command in the logic channel are checked and committed by the safety channel. To minimize the possibility of common errors in both channels, different programming paradigms are used. The logic channel is implemented in a procedural programming language and the Safety-Bag is implemented in PAMELA, a rule-based expert system language suitable for real-time applications. The rule-oriented programming paradigm is very well suited to the Safety-Bag because the safety requirements themselves are represented by rules. The Safety-Bag runs on a standard ALCATEL process control computer.