Thilo S. Gaul

Foundations of Fast Communication via XML

Communication with XML often involves pre-agreed document types. In this paper, we propose an offline parser generation approach to enhance online processing performance for documents conforming to a given DTD. Our examination of DTDs and the languages they define demonstrates the existence of ambiguities. We present an algorithm that maps DTDs to deterministic context-free grammars defining the same languages. We prove the grammars to be LL(1) and LALR(1), making them suitable for standard parser generators. Our experiments show the superior performance of generated optimized parsers. Our results generalize from DTDs to XML schema specifications with certain restrictions, most notably the absence of namespaces, which exceed the scope of context-free grammars.

Correct Programs without Proof? On Checker-Based Program Verification

In many cases, the effort of proving the correctness of large program systems seems not to be justifiable. Since heuristics and programming tricks are used and necessary to solve complex problems successfully, mathematical inductive argumentation often fails, because the algorithms to be verified get too complex and tricky. We need more modular approaches to guarantee program correctness.

Construction of Verified Compiler Front-Ends with Program-Checking

This paper describes how program-checking can be used to establish the correctness of a compiler front-end which was generated by unverified compiler construction tools. The basic idea of programchecking is to use an unverified algorithm whose results are checked by a verified component at run time. The approach not only simplifies the construction of a verified compiler front-end because checking the result of the analysis is much simpler to verify than the verification of a high sophisticated compiler front-end. It even allows to define a notion of front-end correctness. Furthermore, we are still able to use existing generators tools without major modifications. Additionally, this work points out the tasks which still have to be verified and it discusses the flexibility of the approach.

Specification in a large industry consortium-the MOST approach

The MOST Cooperation (media-oriented systems transport) is an industry group of automotive and supplier companies that specifies interfaces of multimedia components. Many members are competitors: they collaborate on standards while preserving their competitive advantages. Moreover, development processes differ for each member, but the MOST standard must be concise and consistent. We develop an XML based architecture to support individual workflows and the specification process as a whole.

Fuzzy-neuro-controlled verified instruction scheduler

We present a fuzzy-neuro approach for instruction scheduling in compilers for modern high performance processors. Instruction scheduling is an optimization problem in NP and is usually addressed with processor dependent heuristics or processor simplifying cost models. The costs for executing a given instruction sequence on the processor can not be determined exactly in practice, because the exact execution model is too complex or simply not available from the manufacturer. Our approach enables the compiler to adapt the cost measure dynamically by learning the processor behavior and typical optimization situations on the basis of reinforcement learning. Additionally, we are able to include fuzzy a priori scheduling knowledge and derive verified implementations by the technique of program checking.