1. Department of Computer Science, University Dortmund, Joseph—von—Fraunhofer—Str. 20, 44227 Dortmund, Germany,
2. Jena Centre for Bioinformatics and Friedrich—Schiller—University Jena, Department of Mathematics and Computer Science, Bio Systems Analysis Group, 07743 Jena, Germany,
3. Department of Computer Science, Memorial University of Newfoundland, St. John's, NL, A1B 3X5, Canada,