SupRB: A Supervised Rule-based Learning System for Continuous Problems

We propose the SupRB learning system, a new Pittsburgh-style learning classifier system (LCS) for supervised learning on multi-dimensional continuous decision problems. SupRB learns an approximation of a quality function from examples (consisting of situations, choices and associated qualities) and is then able to make an optimal choice as well as predict the quality of a choice in a given situation. One area of application for SupRB is parametrization of industrial machinery. In this field, acceptance of the recommendations of machine learning systems is highly reliant on operators' trust. While an essential and much-researched ingredient for that trust is prediction quality, it seems that this alone is not enough. At least as important is a human-understandable explanation of the reasoning behind a recommendation. While many state-of-the-art methods such as artificial neural networks fall short of this, LCSs such as SupRB provide human-readable rules that can be understood very easily. The prevalent LCSs are not directly applicable to this problem as they lack support for continuous choices. This paper lays the foundations for SupRB and shows its general applicability on a simplified model of an additive manufacturing problem.Comment: Submitted to the Genetic and Evolutionary Computation Conference 2020 (GECCO 2020

A closer look at sum-based embeddings for knowledge graphs containing procedural knowledge

While knowledge graphs and their embedding into low dimensional vectors are established fields of research, they mostly cover factual knowledge. However, to improve downstream models, e. g. for predictive quality in real-world industrial use cases, embeddings of procedural knowledge, available in the form of rules, could be utilized. As such, we investigate which properties of embedding algorithms could prove beneficial in this scenario and evaluate which established embedding methodologies are suited to form the basis of sum-based embeddings of different representations of procedural knowledge

Forecasting of residential unit's heat demands: a comparison of machine learning techniques in a real-world case study

A large proportion of the energy consumed by private households is used for space heating and domestic hot water. In the context of the energy transition, the predominant aim is to reduce this consumption. In addition to implementing better energy standards in new buildings and refurbishing old buildings, intelligent energy management concepts can also contribute by operating heat generators according to demand based on an expected heat requirement. This requires forecasting models for heat demand to be as accurate and reliable as possible. In this paper, we present a case study of a newly built medium-sized living quarter in central Europe made up of 66 residential units from which we gathered consumption data for almost two years. Based on this data, we investigate the possibility of forecasting heat demand using a variety of time series models and offline and online machine learning (ML) techniques in a standard data science approach. We chose to analyze different modeling techniques as they can be used in different settings, where time series models require no additional data, offline ML needs a lot of data gathered up front, and online ML could be deployed from day one. A special focus lies on peak demand and outlier forecasting, as well as investigations into seasonal expert models. We also highlight the computational expense and explainability characteristics of the used models. We compare the used methods with naive models as well as each other, finding that time series models, as well as online ML, do not yield promising results. Accordingly, we will deploy one of the offline ML models in our real-world energy management system in the near future

PDPK: A Framework to Synthesise Process Data and Corresponding Procedural Knowledge for Manufacturing

Procedural knowledge describes how to accomplish tasks and mitigate problems. Such knowledge is commonly held by domain experts, e.g. operators in manufacturing who adjust parameters to achieve quality targets. To the best of our knowledge, no real-world datasets containing process data and corresponding procedural knowledge are publicly available, possibly due to corporate apprehensions regarding the loss of knowledge advances. Therefore, we provide a framework to generate synthetic datasets that can be adapted to different domains. The design choices are inspired by two real-world datasets of procedural knowledge we have access to. Apart from containing representations of procedural knowledge in Resource Description Framework (RDF)-compliant knowledge graphs, the framework simulates parametrisation processes and provides consistent process data. We compare established embedding methods on the resulting knowledge graphs, detailing which out-of-the-box methods have the potential to represent procedural knowledge. This provides a baseline which can be used to increase the comparability of future work. Furthermore, we validate the overall characteristics of a synthesised dataset by comparing the results to those achievable on a real-world dataset. The framework and evaluation code, as well as the dataset used in the evaluation, are available open source

Analyse von Ursachen und Co-Faktoren bei frustraner mechanischer Rekanalisation beim ischämischen Schlaganfall

In der vorliegenden Studie wurden die Ursachen der frustranen Thrombektomie bei Patienten mit akutem ischämischem Schlaganfall des vorderen Stromgebietes (A. carotis interna, A. cerebri media) untersucht. Die gesamte Studienpopulation umfasste 100 gescheiterte Interventionen und 100 zufällig ausgewählte Kontrollpatienten aus einer Gesamtheit von 596 am Universitätsklinikum des Saarlandes im Zeitraum Januar 2014 bis Oktober 2018 interventionell therapierten Patienten. Das Kollektiv der beiden Gruppen unterschied sich statistisch nicht in Alter, Geschlecht und der Symptomausprägung. Als erfolgreiche Intervention wurde ein postinterventioneller TICI-Score von 2b oder höher definiert. Es zeigte sich, dass das neurovaskuläre Zentrum in Homburg im Vergleich zur internationalen Literatur vergleichbare Erfolgsraten von etwa 83,2% aufweist. In der Studienpopulation erhöht die intravenöse Lysetherapie vor Intervention die Erfolgsrate signifikant. Außerdem ergab sich ein statistischer Zusammenhang zwischen der dauerhaften Einnahme von Nitraten und einer erfolgreichen Intervention. 20% der gescheiterten Interventionen sind auf technisch mechanische Hindernisse zurückzuführen. Beispielsweise war dabei kein arterieller Zugang zu etablieren oder die Verschlussstelle konnte aufgrund von Stenosen oder Elongationen nicht erreicht werden. In dieser Gruppe konnte eine deutliche Häufung von pAVK und der Einnahme von Acetylsalicylsäure dargelegt werden. Des Weiteren traten bei diesen Patienten technisch-mechanische Hindernisse häufiger bei Verschlüssen der A. carotis interna und seltener in der A. cerebri media, Segment M1 auf. Bei 80% der frustranen Thrombektomien gelang es zwar, den Verschluss zu erreichen, allerdings konnte das Gefäß aus anderen Gründen nicht oder nicht vollständig eröffnet werden. Vorhofflimmern trat bei diesen Patienten seltener auf als in der Kontrollgruppe. Eine Gerinnungsstörung liegt dagegen signifikant häufiger vor. Hinsichtlich der Gerinnungstherapie mit Cumarinen oder Direkten Oralen Antikoagulantien zeigte sich in keiner der Gruppen ein Unterschied. Auch Laborparameter für eine Entzündungsreaktion und die Gerinnung waren in beiden Gruppen vergleichbar. Zeitliche Faktoren bezogen auf Symptombeginn, Lyse und Intervention scheinen für den Rekanalisationserfolg keine Rolle zu spielen, obwohl aus der Literatur bekannt ist, dass sie das Outcome des Patienten stark beeinflussen. Histologische Untersuchungen gewonnener Thromben zeigten – bei einer Fallzahl von nur 6 Proben – keine Differenzen, ebenso wenig wie CT-morphologische Charakteristika des Thrombus. Zusammenfassend lässt sich feststellen, dass etwa 17% aller geplanten Interventionen nach obiger Definition frustran verlaufen. Bei 20% davon, liegt die Ursache in technisch-mechanischen Hindernissen und eine direkte Punktion der Carotiden könnte in einigen Fällen Abhilfe schaffen, um die Verschlussstelle zu erreichen. Bei den übrigen 80% der scheiternden Interventionen liegt die Ursache hauptsächlich in zwei Gründen: Entweder kann trotz erfolgreicher Platzierung des Stent-Retrievers kein Gerinnsel geborgen werden oder es bleibt ein Verschluss distal gelegener Gefäßäste bestehen. Komplikationen, wie Dissektionen und subarachnoidale Blutungen, sind insgesamt selten. Anzumerken ist, dass nur angiographische Daten und keine klinischen Parameter betreffend das Outcome erhoben wurden. Mit 200 Patienten war die untersuchte Fallzahl nicht sehr groß, sodass keine statistische Signifikanz erreicht werden konnte und sich bei vielen Parametern lediglich Tendenzen erkennen lassen. Eine Ausweitung der Studie auf andere Zentren oder eine Wiederholung zu einem späteren Zeitpunkt mit einer größeren Patientenzahl wäre daher wünschenswert.The present study investigated the causes of failing thrombectomy in patients with acute ischemic stroke of the anterior circulation (A. carotis interna, A. cerebri media). The entire study population comprised 100 failed interventions and 100 randomly selected control patients from a total of 596 interventionally treated patients at Saarland University Hospital between January 2014 and October 2018. The collective of the two groups did not differ statistically in age, sex and symptom severity. A postinterventional TICI score of 2b or higher was defined as a successful intervention. It was found that the neurovascular center in Homburg had comparable success rates to the international literature of about 83.2%. In the study population, intravenous thrombolysis before intervention significantly increases the success rate. Furthermore, there was a statistical correlation between the long-term intake of nitrates and a successful intervention. 20% of the failing interventions are due to technical mechanical obstacles. For example, no arterial access could be established, or the occlusion site could not be reached due to stenosis or elongation. In this group, an association with PAOD and the intake of acetylsalicylic acid could be demonstrated. In addition, technical and mechanical obstacles occurred more frequently in occlusions of the internal carotid artery and less frequently in the cerebral media artery, segment M1. In 80% of the frustrated thrombectomies it was possible to reach the occlusion site, but for other reasons the vessel could not or not completely be recanalized. In this group, atrial fibrillation is less frequent than in the control group. In addition, patients with a coagulation disorder have a significantly worse result. Regarding coagulation therapy with coumarins or direct oral anticoagulants, there was no difference in any of the groups. Laboratory parameters for inflammatory response and coagulation were also comparable in both groups. Time factors related to symptom onset, lysis and intervention do not seem to play a role in the success of recanalization, although it is known from the literature that they strongly influence the outcome of the patient. Histological examinations of thrombi obtained - with a case number of only 6 samples - showed no differences, nor did CT-morphological data of the thrombus. In summary, 17% of all interventions fail according to the definition above. In 20% of these, there are technical reasons for failure. Direct carotid puncture could be a solution to reach the occlusion site. In the remainig 80% there are two main causes for failure: On the one hand, no thrombus material can be extracted although the stent-retriever-device is correctly in place and on the other hand, distal vessel branches stay occluded. In total, complications such as subarachnoid hemorrhage or iatrogenic dissection are rare. It should be noted that only angiographic data and no clinical parameters concerning patient outcome were collected. With 200 patients, the investigated case number was not very large, so that no statistic significance could be proven and only tendencies can be identified for many parameters. An extension of the study to other centers or a repetition with a larger number of patients would therefore be necessary

Towards models of conceptual and procedural operator knowledge

To increase the utility of semantic industrial information models we propose a methodology to incorporate extracted operator knowledge, which we assume to be present in the form of rules, in knowledge graphs. To this end, we present multiple modelling patterns that can be combined depending on the required complexity. Aiming to combine information models with learning systems we contemplate desired behaviours of embeddings from a predictive quality perspective and provide a suited embedding methodology. This methodology is evaluated on a real world dataset of a fused deposition modelling process

A framework for modular construction and evaluation of metaheuristics

This paper presents MAHF, a software framework for the highly flexible construction of metaheuristics from individual components and the subsequent evaluation of these algorithms. At that, MAHF is developed specifically for the experimental analysis of the algorithmic behaviour during the optimization process with a focus on the influences of the algorithm’s components. Furthermore, uncommon and incompletely examined operators or frameworks of “novel” metaheuristics are included as well, so that their usefulness can be assessed. In the following, we will elaborate on MAHF’s structure and its general goals and application possibilities. Concerning MAHF’s component structure, we will provide examples of its usage and extension to ensure that it is reusable by others as well