Editorial: ISAAC 2008 Special Issue

This special issue contains a selection of six papers from the 19th Annual International Symposium on Algorithms and Computation (ISAAC 2008), which was held in Gold Coast, Australia on December 15–17, 2008. The ISAAC 2008 program committee accepted 78 papers among 229 high-quality submissions from 40 countries, after a rigorous review process. Among those accepted papers, the following six papers were selected and invited to this special issue, based on their evaluation by the program committee. These six papers all went through the standard refereeing process of Algorithmica before being accepted for publication. The papers in this issue show recent advances in various areas of algorithms and theory of computation research. The first paper, “Signature Theory in Holographic Algorithms” by Cai and Lu, develops the signature theory in holographic algorithms, in terms of d-realizability and d-admissibility. For the class of 2-realizable signatures, they prove a Birkhoff-type theorem which determines this class. This is followed by characterization theorems for 1-realizability and 1-admissibility. Finally, they present some counting problems solvable in polynomial time by holographic algorithms. The second paper, “Faster Parameterized Algorithms for MINIMUM FILL-IN” by Bodlaender, Heggernes and Villanger, presents two parameterized algorithms for the MINIMUM FILL-IN problem, also known as the CHORDAL COMPLETION problem. The first algorithm requires polynomial space, which improves the exponential part