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Liste der Ergebnisse

Preventing Code Insertion Attacks on Token-Based Software Plagiarism Detectors + (Some students tasked with mandatory progra … Some students tasked with mandatory programming assignments lack the time or dedication to solve the assignment themselves. Instead, they plagiarize a peer’s solution by slightly modifying the code. However, there exist numerous tools that assist in detecting these kinds of plagiarism. These tools can be used by instructors to identify plagiarized programs. The most used type of plagiarism detection tools is token-based plagiarism detectors. They are resilient against many types of obfuscation attacks, such as renaming variables or whitespace modifications. However, they are susceptible to inserting lines of code that do not affect the program flow or result.The current working assumption was that the successful obfuscation of plagiarism takes more effort and skill than solving the assignment itself. This assumption was broken by automated plagiarism generators, which exploit this weakness. This work aims to develop mechanisms against code insertions that can be directly integrated into existing token-based plagiarism detectors. For this, we first develop mechanisms to negate the negative effect of many types of code insertion. Then we implement these mechanisms prototypically into a state-of-the-art plagiarism detector. We evaluate our implementation by running it on a dataset consisting of real student submissions and automatically generated plagiarism. We show that with our mechanisms, the similarity rating of automatically generated plagiarism increases drastically. Consequently, the plagiarism generator we use fails to create usable plagiarisms.we use fails to create usable plagiarisms.)
Software Plagiarism Detection on Intermediate Representation + (Source code plagiarism is a widespread pro … Source code plagiarism is a widespread problem in computer science education. To counteract this, software plagiarism detectors can help identify plagiarized code. Most state-of-the-art plagiarism detectors are token-based. It is common to design and implement a new dedicated language module to support a new programming language. This process can be time-consuming, furthermore, it is unclear whether it is even necessary. In this thesis, we evaluate the necessity of dedicated language modules for Java and C/C++ and derive conclusions for designing new ones. To achieve this, we create a language module for the intermediate representation of LLVM. For the evaluation, we compare it to two existing dedicated language modules in JPlag. While our results show that dedicated language modules are better for plagiarism detection, language modules for intermediate representations show better resilience to obfuscation attacks. better resilience to obfuscation attacks.)
Portables Auto-Tuning paralleler Anwendungen + (Sowohl Offline- als auch Online-Tuning ste … Sowohl Offline- als auch Online-Tuning stellen gängige Lösungen zur automatischen Optimierung von parallelen Anwendungen dar. Beide Verfahren haben ihre individuellen Vor- und Nachteile: das Offline-Tuning bietet minimalen negativen Einfluss auf die Laufzeiten der Anwendung, die getunten Parameterwerte sind allerdings nur auf im Voraus bekannter Hardware verwendbar. Online-Tuning hingegen bietet dynamische Parameterwerte, die zur Laufzeit der Anwendung und damit auf der Zielhardware ermittelt werden, dies kann sich allerdings negativ auf die Laufzeit der Anwendung ausüben.Wir versuchen die Vorteile beider Ansätze zu verschmelzen, indem im Voraus optimierte Parameterkonfigurationen auf der Zielhardware, sowie unter Umständen mit einer anderen Anwendung, verwendet werden. Wir evaluieren sowohl die Hardware- als auch die Anwendungsportabilität der Konfigurationen anhand von fünf Beispielanwendungen.ionen anhand von fünf Beispielanwendungen.)
DomainML: A modular framework for domain knowledge-guided machine learning + (Standard, data-driven machine learning app … Standard, data-driven machine learning approaches learn relevant patterns solely from data. In some fields however, learning only from data is not sufficient. A prominent example for this is healthcare, where the problem of data insufficiency for rare diseases is tackled by integrating high-quality domain knowledge into the machine learning process.Despite the existing work in the healthcare context, making general observations about the impact of domain knowledge is difficult, as different publications use different knowledge types, prediction tasks and model architectures. It further remains unclear if the findings in healthcare are transferable to other use-cases, as well as how much intellectual effort this requires.With this Thesis we introduce DomainML, a modular framework to evaluate the impact of domain knowledge on different data science tasks. We demonstrate the transferability and flexibility of DomainML by applying the concepts from healthcare to a cloud system monitoring. We then observe how domain knowledge impacts the model’s prediction performance across both domains, and suggest how DomainML could further be used to refine both the given domain knowledge as well as the quality of the underlying dataset. as the quality of the underlying dataset.)
State of the Art: Multi Actor Behaviour and Dataflow Modelling for Dynamic Privacy + (State of the Art Vortrag im Rahmen der Praxis der Forschung.)
Data-Preparation for Machine-Learning Based Static Code Analysis + (Static Code Analysis (SCA) has become an i … Static Code Analysis (SCA) has become an integral part of modern software development, especially since the rise of automation in the form of CI/CD. It is an ongoing question of how machine learning can best help improve SCA's state and thus facilitate maintainable, correct, and secure software. However, machine learning needs a solid foundation to learn on. This thesis proposes an approach to build that foundation by mining data on software issues from real-world code. We show how we used that concept to analyze over 4000 software packages and generate over two million issue samples. Additionally, we propose a method for refining this data and apply it to an existing machine learning SCA approach.an existing machine learning SCA approach.)
Creating Study Plans by Generating Workflow Models from Constraints in Temporal Logic + (Students are confronted with a huge amount … Students are confronted with a huge amount of regulations when planning their studies at a university. It is challenging for them to create a personalized study plan while still complying to all official rules. The STUDYplan software aims to overcome the difficulties by enabling an intuitive and individual modeling of study plans. A study plan can be interpreted as a sequence of business process tasks that indicate courses to make use of existing work in the business process domain. This thesis focuses on the idea of synthesizing business process models from declarative specifications that indicate official and user-defined regulations for a study plan. We provide an elaborated approach for the modeling of study plan constraints and a generation concept specialized to study plans. This work motivates, discusses, partially implements and evaluates the proposed approach.ments and evaluates the proposed approach.)
A comparative study of subgroup discovery methods + (Subgroup discovery is a data mining techni … Subgroup discovery is a data mining technique that is used to extract interesting relationships in a dataset related to to a target variable. These relationships are described in the form of rules. Multiple SD techniques have been developed over the years. This thesis establishes a comparative study between a number of these techniques in order to identify the state-of-the-art methods. It also analyses the effects discretization has on them as a preprocessing step . Furthermore, it investigates the effect of hyperparameter optimization on these methods. Our analysis showed that PRIM, DSSD, Best Interval and FSSD outperformed the other subgroup discovery methods evaluated in this study and are to be considered state-of-the-art . It also shows that discretization offers an efficiency improvement on methods that do not employ internal discretization. It has a negative impact on the quality of subgroups generated by methods that perform it internally. The results finally demonstrates that Apriori-SD and SD-Algorithm were the most positively affected by the hyperparameter optimization.fected by the hyperparameter optimization.)
Software Testing + (TBA)
Exploring Modern IDE Functionalities for Consistency Preservation + (TBA)
Exploring the Traceability of Requirements and Source Code via LLMs + (TBA)

Data-Driven Approaches to Predict Material Failure and Analyze Material Models + (Te prediction of material failure is usefu … Te prediction of material failure is useful in many industrial contexts such as predictive maintenance, where it helps reducing costs by preventing outages. However, failure prediction is a complex task. Typically, material scientists need to create a physical material model to run computer simulations. In real-world scenarios, the creation of such models is ofen not feasible, as the measurement of exact material parameters is too expensive. Material scientists can use material models to generate simulation data. Tese data sets are multivariate sensor value time series. In this thesis we develop data-driven models to predict upcoming failure of an observed material. We identify and implement recurrent neural network architectures, as recent research indicated that these are well suited for predictions on time series. We compare the prediction performance with traditional models that do not directly predict on time series but involve an additional step of feature calculation. Finally, we analyze the predictions to fnd abstractions in the underlying material model that lead to unrealistic simulation data and thus impede accurate failure prediction. Knowing such abstractions empowers material scientists to refne the simulation models. The updated models would then contain more relevant information and make failure prediction more precise. and make failure prediction more precise.)
Improving SAP Document Information Extraction via Pretraining and Fine-Tuning + (Techniques for extracting relevant informa … Techniques for extracting relevant information from documents have made significant progress in recent years and became a key task in the digital transformation. With deep neural networks, it became possible to process documents without specifying hard-coded extraction rules or templates for each layout. However, such models typically have a very large number of parameters. As a result, they require many annotated samples and long training times. One solution is to create a basic pretrained model using self-supervised objectives and then to fine-tune it using a smaller document-specific annotated dataset. However, implementing and controlling the pretraining and fine-tuning procedures in a multi-modal setting is challenging. In this thesis, we propose a systematic method that consists in pretraining the model on large unlabeled data and then to fine-tune it with a virtual adversarial training procedure. For the pretraining stage, we implement an unsupervised informative masking method, which improves upon standard Masked-Language Modelling (MLM). In contrast to randomly masking tokens like in MLM, our method exploits Point-Wise Mutual Information (PMI) to calculate individual masking rates based on statistical properties of the data corpus, e.g., how often certain tokens appear together on a document page. We test our algorithm in a typical business context at SAP and report an overall improvement of 1.4% on the F1-score for extracted document entities. Additionally, we show that the implemented methods improve the training speed, robustness and data-efficiency of the algorithm.ness and data-efficiency of the algorithm.)
Analyse von Zeitreihen-Kompressionsmethoden am Beispiel von Google N-Grams + (Temporal text corpora like the Google Ngra … Temporal text corpora like the Google Ngram dataset usually incorporate a vast number of words and expressions, called ngrams, and their respective usage frequencies over the years. The large quantity of entries complicates working with the dataset, as transformations and queries are resource and time intensive. However, many use-cases do not require the whole corpus to have a sufficient dataset and achieve acceptable results. We propose various compression methods to reduce the absolute number of ngrams in the corpus. Additionally, we utilize time-series compression methods for quick estimations about the properties of ngram usage frequencies. As basis for our compression method design and experimental validation serve CHQL (Conceptual History Query Language) queries on the Google Ngram dataset. The goal is to find compression methods that reduce the complexity of queries on the corpus while still maintaining good results.rpus while still maintaining good results.)
Analyse von Zeitreihen-Kompressionsmethoden am Beispiel von Google N-Gram + (Temporal text corpora like the Google Ngra … Temporal text corpora like the Google Ngram Data Set usually incorporate a vast number of words and expressions, called ngrams, and their respective usage frequencies over the years. The large quantity of entries complicates working with the data set, as transformations and queries are resource and time intensive. However, many use cases do not require the whole corpus to have a sufficient data set and achieve acceptable query results. We propose various compression methods to reduce the total number of ngrams in the corpus. Specially, we propose compression methods that, given an input dictionary of target words, find a compression tailored for queries on a specific topic. Additionally, we utilize time-series compression methods for quick estimations about the properties of ngram usage frequencies. As basis for our compression method design and experimental validation serve CHQL (Conceptual History Query Language) queries on the Google Ngram Data Set.age) queries on the Google Ngram Data Set.)
Implementation and Evaluation of CHQL Operators in Relational Database Systems + (The IPD defined CHQL, a query algebra that … The IPD defined CHQL, a query algebra that enables to formalize queries about conceptual history. CHQL is currently implemented in MapReduce which offers less flexibility for query optimization than relational database systems does. The scope of this thesis is to implement the given operators in SQL and analyze performance differences by identifying limiting factors and query optimization on the logical and physical level. At the end, we will provide efficient query plans and fast operator implementations to execute CHQL queries in relational database systems.QL queries in relational database systems.)
The Kconfig Variability Framework as a Feature Model + (The Kconfig variability framework is used … The Kconfig variability framework is used to develop highly variable software such as the Linux kernel, ZephyrOS and NuttX. Kconfig allows developers to break down their software in modules and define the dependencies between these modules, so that when a concrete configuration is created, the semantic dependencies between the selected modules are fulfilled, ensuring that the resulting software product can function. Kconfig has often been described as a tool of define software product lines (SPLs), which often occur within the context of feature-oriented programming (FOP). In this paper, we introduce methods to transform Kconfig files into feature models so that the semantics of the model defined in a Kconfig file are preserved. The resulting feature models can be viewed with FeatureIDE, which allows the further analysis of the Kconfig file, such as the detection of redundant dependencies and cyclic dependencies.dant dependencies and cyclic dependencies.)
Review of data efficient dependency estimation + (The amount and complexity of data collecte … The amount and complexity of data collected in the industry is increasing, and data analysis rises in importance. Dependency estimation is a significant part of knowledge discovery and allows strategic decisions based on this information.There are multiple examples that highlight the importance of dependency estimation, like knowing there exists a correlation between the regular dose of a drug and the health of a patient helps to understand the impact of a newly manufactured drug.Knowing how the case material, brand, and condition of a watch influences the price on an online marketplace can help to buy watches at a good price.Material sciences can also use dependency estimation to predict many properties of a material before it is synthesized in the lab, so fewer experiments are necessary.Many dependency estimation algorithms require a large amount of data for a good estimation. But data can be expensive, as an example experiments in material sciences, consume material and take time and energy.As we have the challenge of expensive data collection, algorithms need to be data efficient. But there is a trade-off between the amount of data and the quality of the estimation. With a lack of data comes an uncertainty of the estimation. However, the algorithms do not always quantify this uncertainty. As a result, we do not know if we can rely on the estimation or if we need more data for an accurate estimation.In this bachelor's thesis we compare different state-of-the-art dependency estimation algorithms using a list of criteria addressing these challenges and more. We partly developed the criteria our self as well as took them from relevant publications. The existing publications formulated many of the criteria only qualitative, part of this thesis is to make these criteria measurable quantitative, where possible, and come up with a systematic approach of comparison for the rest.From 14 selected criteria, we focus on criteria concerning data efficiency and uncertainty estimation, because they are essential for lowering the cost of dependency estimation, but we will also check other criteria relevant for the application of algorithms.As a result, we will rank the algorithms in the different aspects given by the criteria, and thereby identify potential for improvement of the current algorithms.We do this in two steps, first we check general criteria in a qualitative analysis. For this we check if the algorithm is capable of guided sampling, if it is an anytime algorithm and if it uses incremental computation to enable early stopping, which all leads to more data efficiency.We also conduct a quantitative analysis on well-established and representative datasets for the dependency estimation algorithms, that performed well in the qualitative analysis.In these experiments we evaluate more criteria:The robustness, which is necessary for error-prone data, the efficiency which saves time in the computation, the convergence which guarantees we get an accurate estimation with enough data, and consistency which ensures we can rely on an estimation.hich ensures we can rely on an estimation.)
Identifying Security Requirements in Natural Language Documents + (The automatic identification of requiremen … The automatic identification of requirements, and their classification according to their security objectives, can be helpful to derive insights into the security of a given system. However, this task requires significant security expertise to perform. In this thesis, the capability of modern Large Language Models (such as GPT) to replicate this expertise is investigated. This requires the transfer of the model's understanding of language to the given specific task. In particular, different prompt engineering approaches are combined and compared, in order to gain insights into their effects on performance. GPT ultimately performs poorly for the main tasks of identification of requirements and of their classification according to security objectives. Conversely, the model performs well for the sub-task of classifying the security-relevance of requirements. Interestingly, prompt components influencing the format of the model's output seem to have a higher performance impact than components containing contextual information.ponents containing contextual information.)
Predicting System Dependencies from Tracing Data Instead of Computing Them + (The concept of Artificial Intelligence for … The concept of Artificial Intelligence for IT Operations combines big data and machine learning methods to replace a broad range of IT operations including availability and performance monitoring of services. In large-scale distributed cloud infrastructures a service is deployed on different separate nodes. As the size of the infrastructure increases in production, the analysis of metrics parameters becomes computationally expensive. We address the problem by proposing a method to predict dependencies between metrics parameters of system components instead of computing them. To predict the dependencies we use time windowing with different aggregation methods and distributed tracing data that contain detailed information for the system execution workflow. In this bachelor thesis, we inspect the different representations of distributed traces from simple counting of events to more complex graph representations. We compare them with each other and evaluate the performance of such methods. evaluate the performance of such methods.)