25,342 research outputs found
Learning probability distributions generated by finite-state machines
We review methods for inference of probability distributions generated by probabilistic automata and related models for sequence generation. We focus on methods that can be proved to learn in the inference
in the limit and PAC formal models. The methods we review are state merging and state splitting methods for probabilistic deterministic automata and the recently developed spectral method for nondeterministic probabilistic automata. In both cases, we derive them from a high-level algorithm described in terms of the Hankel matrix of the distribution to be learned, given as an oracle, and then describe how to adapt that algorithm to account for the error introduced by a finite sample.Peer ReviewedPostprint (author's final draft
The Logic of Language Change
A discussion of the relation of dialectical transitions in Hegel's speculative logic to changes in categories and grammar in the empirical historical languages
Herstellung eines Phaffia rhodozyma : Stamms mit verstĂ€rkter Astaxanthin-Synthese ĂŒber gezielte genetische Modifikation chemisch mutagenisierter StĂ€mme
Ziel dieser Arbeit war es erstmals durch eine Kombination aus chemischer Mutagenese und gezielter genetischer Modifikation (hier: âmetabolic engineeringâ) einen Phaffia-Stamm herzustellen, welcher ĂŒber die Mutagenese hinaus ĂŒber eine weiter verstĂ€rkte Astaxanthin-Synthese verfĂŒgt.
Die von âDSM Nutritional Productsâ bereitgestellten chemischen Mutanten wurden analysiert und ĂŒber einen Selektionsprozess auf PigmentstabilitĂ€t und Wachstum hin optimiert, da die StĂ€mme aus cryogenisierter Dauerkultur starke PigmentinstabilitĂ€ten und ein verzögertes Wachstum aufwiesen.
Ăber eine exploratorische Phase wurde die Carotinoidsynthese analysiert und festgestellt, dass in den Mutanten keine Einzelreaktionen betroffen sind, welche fĂŒr die Heraufregulierung der Carotinoidsynthese in den Mutanten verantwortlich sind. Hierbei wurden Limitierungen identifiziert und diese durch Transformation von Expressionsplasmiden mit geeigneten Genen aufgehoben, um damit eine noch effizientere Metabolisierung von Astaxanthin-Vorstufen hin zu Astaxanthin zu erreichen. Eine Ăberexpression der Phytoensynthase/Lycopinzyklase crtYB resultierte in einem gesteigerten Carotinoidgehalt bei gleichbleibendem Astaxanthin- Anteil. Durch eine zweite Transformation mit einer Expressionskassette fĂŒr die Astaxanthin-Synthase asy konnte der Carotinoidgehalt weiter gesteigert und zusĂ€tzlich eine Limitierung der Metabolisierung von Astaxanthin-Vorstufen behoben werden, sodass die Transformante nahezu alle Intermediate der Astaxanthinsynthese zu Astaxanthin metabolisieren konnte (Gassel et al. 2013). Es konnte gezeigt werden, dass auch in den Mutanten, aus Experimenten mit dem Wildtyp bekannte, Limitierungen identifiziert und ausgeglichen werden konnten
A Grammatical Inference Approach to Language-Based Anomaly Detection in XML
False-positives are a problem in anomaly-based intrusion detection systems.
To counter this issue, we discuss anomaly detection for the eXtensible Markup
Language (XML) in a language-theoretic view. We argue that many XML-based
attacks target the syntactic level, i.e. the tree structure or element content,
and syntax validation of XML documents reduces the attack surface. XML offers
so-called schemas for validation, but in real world, schemas are often
unavailable, ignored or too general. In this work-in-progress paper we describe
a grammatical inference approach to learn an automaton from example XML
documents for detecting documents with anomalous syntax.
We discuss properties and expressiveness of XML to understand limits of
learnability. Our contributions are an XML Schema compatible lexical datatype
system to abstract content in XML and an algorithm to learn visibly pushdown
automata (VPA) directly from a set of examples. The proposed algorithm does not
require the tree representation of XML, so it can process large documents or
streams. The resulting deterministic VPA then allows stream validation of
documents to recognize deviations in the underlying tree structure or
datatypes.Comment: Paper accepted at First Int. Workshop on Emerging Cyberthreats and
Countermeasures ECTCM 201
Phrase structure grammars as indicative of uniquely human thoughts
I argue that the ability to compute phrase structure grammars is indicative of a particular kind of thought. This type of thought that is only available to cognitive systems that have access to the computations that allow the generation and interpretation of the structural descriptions of phrase structure grammars. The study of phrase structure grammars, and formal language theory in general, is thus indispensable to studies of human cognition, for it makes explicit both the unique type of human thought and the underlying mechanisms in virtue of which this thought is made possible
The Narrow Conception of Computational Psychology
One particularly successful approach to modeling within cognitive science is computational psychology. Computational psychology explores psychological processes by building and testing computational models with human data. In this paper, it is argued that a specific approach to understanding computation, what is called the ânarrow conceptionâ, has problematically limited the kinds of models, theories, and explanations that are offered within computational psychology. After raising two problems for the narrow conception, an alternative, âwide approachâ to computational psychology is proposed
Linguistic Judgments As Evidence
An overview of debates surrounding the use of meta-linguistic judgments in linguistics, including recent relevant empirical results
The universality of categories and meaning: a Coserian perspective
Studies in linguistic typology have challenged the idea that languages can be analyzed in terms of a set of preestablished universal categories. Each language should instead be described âin its own terms,â a view consistent with the âoldâ structuralist paradigm in linguistics. The renewed orientation toward differences between languages raises two questions: (i) How do we identify the meanings which are assumed to be crosslinguistically comparable? (ii) What is the relationship between language-particular categories and comparative concepts commonly used in linguistic typology? To answer these questions, this article focuses on a number of distinctions advocated by Eugenio Coseriu (1921â2002). Coseriu distinguishes three levels of meaning (designation, âsignifiĂ©s,â and sense) and three types of universals (essential, empirical, and possible universals). Their relevance for linguistic typology is discussed with regard to the expression of possession and a particular diathesis in Japanese, viz. ukemi or âindirect passive.â As well as relating language-particular categories and comparative concepts, Coseriuâs approach offers a promising avenue to account for the ways language-specific meanings interact with extralinguistic knowledge and contents of discourse and texts, which are the object of translation
- âŠ