Michael Elberfeld

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Bodlaender's Theorem states that for every k there is a linear-time algorithm that decides whether an input graph has tree width k and, if so, computes a width-k tree composition. Courcelle's Theorem builds on Bodlaender's Theorem and states that for every monadic second-order formula φ and for every k there is a linear-time algorithm that decides(More)
Parameterized complexity theory measures the complexity of computational problems predominantly in terms of their parameterized time complexity. The purpose of the present paper is to demonstrate that the study of parameterized space complexity can give new insights into the complexity of well-studied parameterized problems like the feedback vertex set(More)
An algorithmic meta theorem for a logic and a class C of structures states that all problems expressible in this logic can be solved efficiently for inputs from C. The prime example is Courcelle’s Theorem, which states that monadic second-order (mso) definable problems are linear-time solvable on graphs of bounded tree width. We contribute new algorithmic(More)
Graph orientation is a fundamental problem in graph theory that has recently arisen in the study of signaling-regulatory pathways in protein networks. Given a graph and a list of ordered source-target vertex pairs, it calls for assigning directions to the edges of the graph so as to maximize the number of pairs that admit a directed source-to-target path.(More)
We study on which classes of graphs first-order logic (<scp>fo</scp>) and monadic second-order logic (<scp>mso</scp>) have the same expressive power. We show that for all classes C of graphs that are closed under taking subgraphs, <scp>fo</scp> and <scp>mso</scp> have the same expressive power on C if and only if, C has bounded tree depth. Tree depth is a(More)
The parameterized complexity of a problem is generally considered “settled” once it has been shown to be fixed-parameter tractable or to be complete for a class in a parameterized hierarchy such as the weft hierarchy. Several natural parameterized problems have, however, resisted such a classification. In the present paper we argue that, in some cases, this(More)
To investigate the occurrence of West Nile virus (WNV) and Eastern equine encephalitis virus (EEE) in southeastern Virginia, the Bureau of Laboratories at the Norfolk Department of Public Health (NDPH) analyzed mosquito pools and the sera of sentinel chickens from the southeastern Virginia area each year from 2000 to 2004. Mosquito pool supernatants were(More)
A string-based negative selection algorithm is an immune-inspired classifier that infers a bipartitioning of a string space Σ from a training set S containing samples from only one of the partitions. The algorithm generates a set of patterns, called “detectors”, to cover regions of the string space containing none of the training samples. These patterns are(More)