Frank Rittinger

HOL-Z 2.0: A Proof Environment for Z-Specifications

We present a new proof environment for the specification language Z. The basis is a semantic representation of Z in a structure-preserving, shallow embedding in Isabelle/HOL. On top of the embedding, new proof support for the Z schema calculus and for proof structuring are developed. Thus, we integrate Z into a well-known and trusted theorem prover with advanced deduction technology such as higher-order rewriting, tableaux-based provers and arithmetic decision procedures. A further achievement of this work is the integration of our embedding into a new tool-chain providing a Z-oriented type checker, documentation facilities and macro support for refinement proofs; as a result, the gap has been closed between a logical embedding proven correct and a tool suited for applications of non-trivial size.

The CS Freiburg Robotic Soccer Team: Reliable Self-Localization, Multirobot Sensor Integration, and Basic Soccer Skills

Robotic soccer is a challenging research domain because problems in robotics, artificial intelligence, multi-agent systems and real-time reasoning have to be solved in order to create a successful team of robotic soccer players. In this paper, we describe the key components of the CS Freiburg team. We focus on the self-localization and object recognition method based on using laser range finders and the integration of all this information into a global world model. Using the explicit model of the environment built by these components, we have implemented path planning, simple ball handling skills and basic multi-agent cooperation. The resulting system is a very successful robotic soccer team, which has not lost any game yet.

A Formal Analysis of the CORBA Security Service

We give a formal specification and analysis of the security service of CORBA, the Common Object Request Broker Architecture specified by the Object Management Group, OMG. In doing so, we tackle the problem of how one can apply lightweight formal methods to improve the precision and aid the analysis of a substantial, committee-designed, informal specification. Our approach is scenario-driven: we use representative scenarios to determine which parts of the informal specification should be formalized and verify the resulting formal specification against these scenarios. For the formalization, we have specified a significant part of the security services data-model using the formal language Z. Through this process, we have been able to sharpen the OMG-specification, uncovering a number of errors and omissions.

The CS Freiburg Team Playing Robotic Soccer Based on an Explicit World Model

Robotic soccer is an ideal task to demonstrate new techniques and explore new problems. Moreover, problems and solutions can easily be communicated because soccer is a well-known game. Our intention in building a robotic soccer team and participating in RoboCup-98 was, first, to demonstrate the usefulness of the self-localization methods we have developed. Second, we wanted to show that playing soccer based on an explicit world model is much more effective than other methods. Third, we intended to explore the problem of building and maintaining a global team world model. As has been demonstrated by the performance of our team, we were successful with the first two points. Moreover, robotic soccer gave us the opportunity to study problems in distributed, cooperative sensing.

A formal data-model of the CORBA security service

We use the formal language Z to specify and analyze the security service of CORBA. In doing so, we tackle the problem of how one can apply lightweight formal methods to improve the precision and aid the analysis of a substantial, informal specification. Our approach is scenario-driven: we use representative scenarios to determine which parts of the informal specification should be formalized and then verify the formal specification against the requirements of these scenarios.