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Diese Arbeit befasst sich mit epistemologischen Überzeugungen von Lehramtsstudierenden in der Disziplin Erziehungswissenschaft. Das Konstrukt der epistemologischen Überzeugungen wird zunächst in einer historischen Synopse in seiner Entwicklung beleuchtet, wobei drei unterschiedliche Phasen der Konstruktgenese unterschieden werden können. Die zentralen Konzeptualisierungen epistemologischer Überzeugungen werden dargestellt. Aufbauend auf den jüngsten Erkenntnissen im Feld wird eine aktuelle Synthese vorgenommen, aus der sowohl wissenschaftlicher Anlass als auch praktischer Bedarf zu einer auf die Disziplin fokussierten Instrumententwicklung abgeleitet werden. Vor empirisch-methodologischem Hintergrund wird die klassische Testtheorie als geeignetes Methodenspektrum für die Instrumententwicklung herangezogen. Im Hinblick auf die inzwischen vorherrschende Forschungsauffassung, dass es sich bei den epistemologischen Überzeugungen um ein mehrdimensionales und disziplinspezifisches Konstrukt handelt, werden die aus dem Theoriegefüge gewonnenen Dimensionen zu einem Instrument, dem StEB (students' epistemological beliefs) Inventar, welches in drei aufeinanderfolgenden Studien entwickelt, geprüft, modifiziert und dessen Testwertinterpretationen validiert werden. Auf eine überregionale, formalisierte Expertenbefragung folgt eine zur EFA geeignete erste Untersuchung. Die darauf aufbauende Instrumentmodifikation wird in einer zweiten Stichprobe geprüft, die zugleich auch Validierungsstichprobe ist. Erneut werden die Modelle in dieser zweiten Stichprobe hinsichtlich Dimensionalität, Faktorladungen und Modellgüte mittels CFA und EFA getestet. Die Validierung folgt dem argumentationsbasierten Ansatz. Aus den Testwertinterpretationen leiten sich empirisch prüfbare Grundannahmen über den Testinhalt, die interne Teststruktur, die Beziehungen der StEB Testwerte mit Lernstrategien sowie angenommene Gruppenunterschiede ab. Die Prüfung der Grundannahmen stellt Evidenzen bereit, die die Gültigkeit der Testwertinterpetationen stützen. Das Resultat ist ein in Forschung und Praxis einsatzbereites, mehrdimensionales und disziplinspezifisches, quantitatives Erhebungsinstrument. Abschließend werden die forschungspragmatischen und praktischen Implikationen für das Feld der Erziehungswissenschaft und der Lehrerbildung diskutiert.
Zum Verhältnis von Interesse und Lebensweltbezug bei Lernaufgaben im Unterrichtsfach Geschichte
(2018)
Die geschichtsdidaktische wie allgemeindidaktische Theorie postulieren Lebensweltbezüge als interessenförderliches Merkmal von Unterricht und Lernaufgaben (Gautschi 2011; Waldis&Buff 2007; Bergmann 2002; Kleinknecht et al. 2012). In der Studie wird zunächst das theoretische Konzept des Lebensweltbezugs im Kontext des historischen Lernens diskutiert und für die Hypothesenprüfung operationalisiert.
Für die empirische Untersuchung der Wirksamkeitsannahmen des Lebensweltbezugs von Geschichtsaufgaben wird das situationale Interesse als zweidimensionales Konstrukt bestehend aus Aufgabeninteressantheit und subjektiver Bedeutsamkeit der Aufgabe (vgl. auch Hidi&Renninger 2012; Durik&Harackievicz 2007; Mitchell 1993) konzeptualisiert. Dabei wird davon ausgegangen, dass sich Merkmale der Aufgabe auf beide Komponenten des situationalen Interesses unterschiedlich auswirken können. Zusätzlich wird ein Einfluss des individuellen Fachinteresses an Geschichte auf die Aufgabenwahrnehmung angenommen.
Eine differenzielle Betrachtung des Interesses (Fachinteresse und situationales Interesse) für das Fach Geschichte stellt bislang ein Desiderat dar. Sowohl auf Aufgaben- wie auch auf Individualebene liegen hierzu nur wenige Befunde für das historische Lernen vor (Bracke et al. 2014). Ebenso lässt sich die interessenförderliche Wirkung des Lebensweltbezugs für Geschichte bislang nur unzureichend empirisch belegen.
Für die Studie wurden insgesamt 34 Aufgaben zu drei Themengebieten des Geschichtsunterrichts der 9. Jahrgangsstufe inhaltsanalytisch hinsichtlich ihres Lebensweltbezugs untersucht sowie 801 Schüler/innen bayerischer Realschulen hinsichtlich der wahrgenommenen Interessantheit und Bedeutsamkeit der Aufgaben befragt.
Die Wirkung des jeweiligen Lebensweltbezugs sowie des individuellen Fachinteresses auf die wahrgenommene subjektive Bedeutsamkeit und Interessantheit der Aufgaben wurde mittels Cross-Classified Mulitlevel Analysen mit dem Statistikprogramm MPlus (Muthén und Muthén 2012) überprüft.
Die Analysen zeigten, dass grundsätzlich das bereits bestehende Fachinteresses Geschichte eines Menschen die wahrgenommene Interessantheit und Bedeutsamkeit der Aufgabe prädiziert, unabhängig von den Merkmalen der Aufgabe. Die differenzielle Wirkung von Aufgabenmerkmalen auf die beiden Komponenten des situationalen Interesses kann den Ergebnissen gemäß bestätigt werden. Insgesamt gesehen wirkt der Lebensweltbezug einer Aufgabe insbesondere auf die subjektive Bedeutsamkeit und nicht auf die Aufgabeninteressantheit.
Es wird diskutiert, dass das Fachinteresse an Geschichte als Prädiktorvariable eine wichtige Einflussgröße auf die Aufgabenwahrnehmung darstellt. Zugleich ist das situationale Interesse, das beim Lernen geweckt wird, eine wichtige Voraussetzung dafür, dass sich dauerhaft ein stabiles individuelles Fachinteresse ausbilden kann (Ferdinand 2014).
In der geschichtsdidaktischen Forschung wurde den motivationalen Bedingungen des historischen Lernens insgesamt bislang nur wenig Aufmerksamkeit beigemessen. Die Ergebnisse der Studie legen nahe, dass eine intensivere Erforschung einer interessenförderlicher Unterrichts- und Aufgabengestaltung, die sowohl die situationale Interessantheit als auch die subjektive Bedeutsamkeit anregt, einen wertvollen Beitrag zur Erweiterung des empirischen Forschungsfeldes in der Geschichtsdidaktik leisten kann.
Die Bergrechtsreformen Mitte des 19. Jh. in Preußen hatten weitreichende Auswirkungen auf die Bergarbeiterschaft. In Nordrhein-Westfalen wurde 1994 mit dem Wechsel von der Gewerbeaufsicht zur Arbeitsschutzverwaltung ein ähnlicher Paradigmenwechsel vollzogen. Die Abhandlung untersucht und vergleicht die Auswirkungen dieser Rechtsänderungen.
This thesis distills technical requirements for an increased probative value and data protection compliance, and maps them onto cryptographic properties for which it constructs provably secure and especially private malleable signature schemes (MSS). MSS are specialised digital signature schemes that allow the signatory to authorize certain subsequent modifications, which will not negatively affect the signature verification result.
Legally, regulations such as European Regulation 910/2014 (eIDAS), ‘follow-up’ to longstanding Directive 1999/93/EC, describe the requirements in technology-neutral language. eIDAS states that, when a digital signature meets the full requirements it becomes a qualified electronic signature and then it “[...] shall have the equivalent legal effect of a handwritten signature [...]” [Art. 25 Regulation 910/2014]. The question of what legal effect this has with regards to the probative value that is assigned is actually not determined in EU Regulation 910/2014 but in European member state law. This thesis concentrates in its analysis on the — in this respect detailed — German Code of Civil Procedure (ZPO). Following the ZPO, a signature awards the signed document with at least a high probative value of prima facie evidence. For signed documents of official authority the ZPO’s statutory rules even award evidence with a legal presumption of authenticity. This increased probative value is also awarded to electronic documents bearing electronic signatures when those conform to the eIDAS requirements. The requirements centre around the technical security goals of integrity and accountability. Technical mechanisms use cryptographic means to detect the absence of unauthorized modifications (integrity) and allow to authenticate the signed document’s signatory (accountability).
However, the specialised malleable signature schemes’ main advantage is a cryptographic property termed privacy: An authorized subsequent modification will protect the confidentiality of the modified original. Moreover, the MSS will retain a verifiable signature if only authorized modifications were carried out. If these properties are reached with provable security the schemes are called private malleable signature schemes. This thesis analyses two forms of MSS discussed in existing literature: Redactable signature schemes (RSS) which allow subsequent deletions, and sanitizable signature schemes (SSS) which allow subsequent edits. These two forms have many application scenarios: A signatory can delegate that a later redaction might take place while retaining the integrity and authenticity protection for the still remaining parts. The verification of a signature on a redacted or sanitized document still enables the verifying entity to corroborate the signatory’s identity with the help of flanking technical and organisational mechanisms, e.g. a trusted public key infrastructure. The valid signature further corroborates the absence of unauthorized changes, because the MSS is still cryptographically protecting the signed document from undetected unauthorized changes inflicted by adversaries. Due to the confidentiality protection for the overwritten parts of the document following from cryptographic privacy the sanitization and redaction can be used to safeguard personal data to comply with data protection regulation or withhold trade-secrets.
The research question is: Can a malleable signature scheme be private to be compliant with EU data protection regulation and at the same time fulfil the integrity protection legally required in the EU to achieve a high probative value for the data signed?
Answering this requires to understand the protection requirements in respect to accountability and integrity rooted in Regulation 910/2014 and related legal texts. This thesis has analysed the previous Directive 1999/93/EC as well as German SigG and SigVO or UK and US laws. Besides that, legal texts, laws and regulations for the protection requirements of personal data (or PII) have been analysed to distill the confidentiality requirements, e.g. the German BDSG or the EU Regulation 2016/679 (GDPR). Moreover, an answer to the research question entails understanding the relevant difference between regular digital signature schemes, like RSASSA-PSS from PKCS-v2.2 [422], which are legally accepted mechanisms for generating qualified electronic signatures and MSS for which the legal status was completely unknown before the thesis. Especially as MSS allow the authorized entity to adapt the signature, such that it is valid after the authorized modification, without the knowledge or use of the signatory’s signature generation key. On verification of an MSS the verifying entity still sees a valid signature technically appointing the legal signatory as the origin of a document, which might — however — have undergone authorized modifications after the signature was applied.
The thesis documents the results achieved in several domains:
1. Analysis of legal requirements towards integrity protection for an increased probative value and towards the confidentiality protection for use as a privacy-enhancing-technique to comply with data protection regulation.
2. Definition of a suitable terminology for integrity protection to capture (a) the differences between classical and malleable signature schemes, (b) the subtleties among existing MSS, as well as (c) the legal requirements.
3. Harmonisation of existing MSS and their cryptographic properties and the analysis of their shortcomings with respect to the legal requirements.
4. Design of new cryptographic properties and their provably secure cryptographic instantiations, i.e., the thesis proposes nine new cryptographic constructions accompanied by rigorous proofs of their security with respect to the formally defined cryptographic properties.
5. Final evaluation of the increased probative value and data-protection level achievable through the eight proposed cryptographic malleable signature schemes.
The thesis concludes that the detection of any subsequent modification (authorized and unauthorized) is of paramount legal importance in order to meet EU Regulation 910/2014. Further, this thesis formally defined a public form of the legally requested integrity verification which allows the verifying entity to corroborate the absence of any unauthorized modifications with a valid signature verification while simultaneously detecting the presence of an authorized modification — if at least one such authorized modification has subsequently occurred. This property, called non-interactive public accountability (PUB), has been formally defined in this thesis, was published and has already been adopted by the academic community. It was carefully conceived to not negatively impact a base-line level of privacy protection, as non-interactive public accountability had to destroy an existing strong privacy notion of transparency, which was identified as a hinderance to legal equivalence arguments. With RSS and SSS constructions that meet these properties, the thesis can give a positive answer to the research question:
Private MSS can reach a level of integrity protection and guarantee a level of accountability comparable to that of technical mechanisms that are legally accepted to generate qualified electronic signatures giving an increased probative value to the signed document, while at the same time protect the overwritten contents’ confidentiality.
This work illustrates reform approaches in Africa using an international legal comparative approach. The research uses Tanzania and Senegal as the primary case studies and France, the United Kingdom and Germany as secondary case studies to illustrate how Europe reformed data protection regimes through the transposition of the EU Data Protection Directive of 1995.
Chapter one introduces the work; explaining the forces towards data protection regulations and their basis. Chapter two provides for a ‘back-to-back' comparison in three countries (France, Germany and United Kingdom) against the 1995 Data Protection Directive. The idea behind this chapter is to draw a picture on how the legal culture and the pre-existing notions of the right to privacy inform on data protection legal reforms and determines the nature, contents, context and interpretation of adopted regime for data protection. Eventually, all these aspects affect the nature and extent of protection offered regardless of the substance of the law adopted.
Chapter three gives a narrative explanation of nature and perceptions of the right to privacy in Africa and how this may affect data protection reforms in Africa. In the same disposition, African customary legal systems and practices are explained providing a reader with a picture of the overall nature of African systems that makes up an African legal culture. The overview of African privacy perception and legal system is necessary for assessing the workability of any data protection regime to be adopted in Africa which in effect answers the first research question. The chapter draws its rationale from chapter two. In understanding African perceptions of privacy and the African legal culture, one can be able to predict the content and context of the reforms and maybe how the judiciary might interpret the laws based on local perceptions and supporting systems.
An overview of the African data protection architecture or rather human right architecture is provided in chapter four; ideally to provide a reader with a picture of the enforcement systems in Africa as a continent. This is followed by chapter five discussing the two major legal systems in Africa; the civil law and the common law system. The chapter also illustrates the position of African landscape in relation to legal harmonization/unification. This aspect is considered necessary because data protection regimes are more focused on legal harmonization and hence the question of how well or to what extent Africa as a continent can bring about harmonization in law became inevitable. Eventually, the chapter offers a comparative mirror analysis of the primary case studies, i.e. Senegal and Tanzania. The analysis is made on the reform approach taken, motivation behind the reforms and on the regime erected (this is done through textual analysis of the law and the draft bill respectively).
Chapter six concludes the work by answering research questions based on findings and scrutiny from each chapter. It is concluded that there is a very slim chance for the African States to cling on the cultural defence against the adoption of the Western frameworks for data protection. It is also concluded that, lest Africa becomes an active participant in the global process that informs on data protection challenges and regulations, it faces a danger of becoming a puppet of foreign data protection regulation, which may or may not fit African legal culture. The chapter also illustrates how Africa as a continent and the African States individually have taken up data protection reforms blindly. The motivations for the reforms are vaguely stated and unclear. In the majority of legal instruments, the reforms are not taken as a move towards securing and protecting individual rights rather a purely political move influenced by economic motivations. The reforms are to a large extent, a mere impression to align with global data protection regimes and hence lack the political will to enforce the laws.
Optical Graph Recognition
(2017)
Graphs are an important model for the representation of structural information between objects. One identifies objects and nodes as well as a binary relation between objects and edges. Graphs have many uses, e. g., in social sciences, life sciences and engineering. There are two primary representations: abstract and visual. The abstract representation is well suited for processing graphs by computers and is given by an adjacency list, an adjacency matrix or any abstract data structure. A visual representation is used by human users who prefer a picture. Common terms are diagram, scheme, plan, or network. The objective of Graph Drawing is to transform a graph into a visual representation called the drawing of a graph. The goal is a “nice” drawing.
In this thesis we introduce Optical Graph Recognition. Optical Graph Recognition (OGR) reverses Graph Drawing and transforms a digital image of a graph into an abstract representation. Our approach consists of four phases: Preprocessing where we determine which pixels of an image are part of the graph, Segmentation where we recognize the nodes, Topology Recognition where we detect the edges and Postprocessing where we enrich the recognized graph with additional information. We apply established digital image processing methods and make use of the special property that the image contains nodes that are connected by edges. We have focused on developing algorithms that need as little parameters as possible or to automatically calibrate the parameters. Most false recognition results are caused by crossing edges as this makes tracing the edges difficult and can lead to other recognition errors.
We have evaluated hand-drawn and computer-drawn graphs. Our algorithms have a very high recognition rate for computer-drawn graphs, e. g., from a set of 100000 computer-drawn graphs over 90% were correctly recognized. Most false recognition results where observed for hand-drawn graphs as they can include drawing errors and inaccuracies. For universal usability we have implemented a prototype called OGRup for mobile devices like smartphones or tablet computers. With our software it is possible to directly take a picture of a graph via a built in camera, recognize the graph, and then use the result for further processing. Furthermore, in order to gain more insight into the way a person draws a graph by hand, we have conducted a field study.
The influence of situational interest on the appropriate use of cognitive learning strategies
(2017)
This study explores the role of two facets of situational interest, interestingness and
personal significance, as predictors of the adequate use of three types of cognitive
learning strategies (rehearsal strategies, organizational strategies, and elaboration
strategies). In order to attain this goal, it introduces a new measure of the adequacy
of the use of cognitive learning strategies by using the distance between teachers’
estimates of appropriate use of learning strategies for a specific task and students’
reported strategic behavior.
Based on a theoretical model of the use of cognitive learning strategies, the study
shows, by means of structural equation modeling, that different facets of situational
interest play different roles in predicting students’ surface and deep processing. In
summary, it was found that experienced personal significance played a major role
in predicting deep-processing strategies for a significant proportion of the 34 tasks
in this study, whereas interestingness fell short of expectations.
Limitations did arise owing to some missing values, which may blur the findings at
the lower interest and achievement end for the student sample. Nevertheless, suggestions
have been made for future research, which can help teachers of history
classes to determine components of success, namely experienced personal significance,
when designing tasks and consequently provide effective learning tasks to
their classes.
Eine duale Karriere stellt eine Quelle vielfältiger Anforderungen und Belastungen dar. Im Rahmen dieser Studie soll geklärt werden, ob und in welchem Ausmaß jugendliche NachwuchsleistungssportlerInnen in Bayern ein chronisches Stressempfinden aufweisen. Multivariate Varianzanalysen ergaben eine überdurchschnittliche Stressbelastung der AthletenInnen. Zudem erwiesen sich das schulische Selbstkonzept, der totale Effekt des globalen Selbstwerts sowie die Fürsorglichkeit des Trainers als bedeutendste Ressourcen. Die Ergebnisse dieser Studie geben Anlass für eine regelmäßige Stressdiagnose und der Implementation entsprechender Präventionsmaßnahmen im bayerischen Nachwuchsleistungssport.
German state elections are in focus of this work due to the decreasing importance of the "catch all parties" and rise of the AfD in 2013. As small parties like the AfD first reached the 5% threshold in state parliaments (e.g. in the Saxony state election 2014), state elections can be used as barometer elections for the national ones. Further, state elections fill the gap between the 4-year national election cycle and provide additional information for the national election.
The aim of this thesis is to forecast state elections based on polling data from different institutes. Despite occurring errors in polls like measurement or sampling errors - which are also discussed in this work - forecasting is made with aggregate models depending on short term polling data. Irregular polling data have to be customized to generate daily data to apply parametric regression based models. To forecast single vote shares in multi-party elections, the range of methods varies from basic methods like averaging over nonparametric regression based methods to dynamic linear models.
Software model checking is a successful technique for automated program verification. Several of the most widely used approaches for software model checking are based on solving first-order-logic formulas over predicates using SMT solvers, e.g., predicate abstraction, bounded model checking, k-induction, and lazy abstraction with interpolants. We define a configurable framework for predicate-based analyses that allows expressing each of these approaches. This unifying framework highlights the differences between the approaches, producing new insights, and facilitates research of further algorithms and their combinations, as witnessed by several research projects that have been conducted on top of this framework. In addition to this theoretical contribution, we provide a mature implementation of our framework in the software verifier that allows applying all of the mentioned approaches to practice. This implementation is used by other research groups, e.g., to find bugs in the Linux kernel, and has proven its competitiveness by winning gold medals in the International Competition on Software Verification.
Tools and approaches for software model checking like our predicate analysis are typically evaluated using performance benchmarking on large sets of verification tasks. We have identified several pitfalls that can silently arise during benchmarking, and we have found that the benchmarking techniques and tools that are used by many researchers do not guarantee valid results in practice, but may produce arbitrarily large measurement errors. Furthermore, certain hardware characteristics can also have nondeterministic influence on the measurements. In order to being able to properly evaluate our framework for software verification, we study the effects of these hardware characteristics, and define a list of the most important requirements that need to be ensured for reliable benchmarking. We present as solution an open-source benchmarking framework BenchExec, which in contrast to other benchmarking tools fulfills all our requirements and aims at making reliable benchmarking easy. BenchExec was already adopted by several research groups and the International Competition on Software Verification.
Using the power of BenchExec we conduct an experimental evaluation of our unifying framework for predicate analysis. We study the effect of varying the SMT solver and the way program semantics are encoded in formulas across several verification algorithms and find that these technical choices can significantly influence the results of experimental studies of verification approaches. This is valuable information for both researchers who study verification approaches as well as for users who apply them in practice. Our comprehensive study of 120 different configurations would not have been possible without our highly flexible and configurable unifying framework for predicate analysis and shows that the latter is a valuable base for conducting experiments. Furthermore, we show using a comparison against top-ranking verifiers from the International Competition on Software Verification that our implementation is highly competitive and can outperform the state of the art.