About Us



The weblog contains primarily commentary on and analysis of safety-related matters with complex systems, especially those involving digital components. Our writers have academic and professional experience with accident analyses, in particular with aircraft accidents, and are in the forefront of developing analysis methods.

PBL is also a trained logician, and maintains interest in applied logic and philosophy.

Our academic WWW site is www.rvs.uni-bielefeld.de and there are technical papers and downloadable software on the Causalis Limited WWW site


PBL is Peter Bernard Ladkin, Professor of Computer Networks and Distributed Systems in the Faculty of Technology at the University of Bielefeld; Principal Investigator in the university’s Cognitive Interaction Technology Center of Excellence CITEC; founder and a director of the tech-transfer company Causalis Limited.

Peter and Causalis Limited specialise in the analysis of safety-related and safety-critical complex heterogeneous systems and their behavior, including accidents. His group at CITEC investigates safety and security issues with human-machine interactions and develops methods for safety assurance. He developed Why-Because Analysis (WBA) for the causal analysis of accidents and incidents in 1996-8 with the assistance of students. WBA has been adopted as a company standard by Siemens Transportation Systems Rail Automation Division, the world market-leader in railway signalling systems, as well as by Siemens Transportation Systems Mass Transit, a leading supplier of trams and tramway systems. It is also used by the two leading academic institutions in Germany which analyse rail accidents. It has supported prominent legal proceedings in New Zealand, Japan, Indonesia, England and France as well as insurance negotiations on major accidents. WBA software tools are available. Peter has also developed a rigorous safety analysis method Ontological Hazard Analysis (OHA), based on formal specification and formal refinement, to determine safety requirements for critical systems as completely as possible.

Peter has a B.A. (Hons) degree in Maths and Philosophy from the University of Oxford, an M.A. in Mathematics and a Ph.D. in Logic and the Methodology of Science, both from the University of California at Berkeley. He has taught math and computer science inter alia at Stanford University and the University of California at Berkeley, and at Bielefeld since 1995. He has held visiting professorships in Germany, France, Britain and Canada, and has worked in California at the SRI International Computer Science Laboratory and the Kestrel Institute as well as consulting for Silicon Valley companies. In 2002, he co-founded the Bieleschweig Workshops in System Engineering with colleagues in Braunschweig. He serves on numerous program committees for international conferences, and has given invited addresses to major computer-safety conferences such as SAFECOMP, the Safety-Critical Systems Symposium, and the IET International System Safety Conference (Oct 2009). He holds a U.S. FAA private pilot’s licence with instrument rating, has about 750 hrs TT and used to own a PA28-181 which he has flown all over the Western U.S. and Southwestern deserts. He doesn’t own a car, but has numerous bicycles.

Peter may be contacted at ladkinATrvsDOTuni-bielefeldDOTde

bsieker is Dr.-Ing. Bernd Sieker of the University of Bielefeld’s Centre of Excellence in Cognitive Interaction Technology, CITEC. He is also Senior Reverse Engineer of Causalis Limited, the principal developer of the first software suite for Why-Because Analysis, VWBT, and the implementor of the local area network (LAN) for VWBT which Causalis has used for WBA tutorials internationally. His doctoral thesis concerned the safety analysis using Ontological Hazard Analysis (OHA) of the protocol for train dispatching (a verbal protocol used on lightly-travelled lines without signals) in German rail operations. His work has been presented in an Informatics Colloquium at the University of Kiel in 2006, as an all-day industrial tutorial for the Safety-Critical Systems Club in London in 2006, and in an invited talk to the Safety-Critical Systems Symposium in Brighton in 2009. He has performed numerous Why-Because Analyses and Hazard Analyses for clients of Causalis as well as pro bono. Samples of such work may be found on the Publications section of the Causalis WWW site.

Bernd may be contacted at siekerATcausalisDOTcom

JS is Dr.-Ing. Jan Sanders. Jan has a degree in Informatics for Natural Science from Bielefeld, specialising in Cognitive Science and Communications Theory. He currently works for the Bundesamt für Sicherheit in der Informationstechnik (BSI), the Federal Information-Technology Security Agency, in the area of infrastructure security. He is the lead programmer of the SERAS software tool suite for causal analysis of incidents and accidents.

Jan may be contacted at janATrvsDOTuni-bielefeldDOTde