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Uta Störl

Publications and source records attributed to Uta Störl.

12 recordsLinked to original sources

Rethinking Accuracy: A Weighted Error-Based Metric for Data Quality

Real data often contains errors, which is why data engineers spend a lot of time creating data cleaning pipelines to ensure the best possible data quality. However, it is often difficult to compare the results of different pipelines and decide which pipeline leads to the best results. There are many different metrics that are designed for different use cases, but they often take only a portion of the data into account. There is a lack of universally applicable metrics for measuring data quality that can be used in many different scenarios. That is why in this paper we are presenting TOMME - an initial approach to a universally applicable weighted error-based metric for data quality. This allows the data quality of a dataset to be assessed based on a single score. While a detailed data quality evaluation remains important, the use of a single score enables rapid assessment and automated processing, for example, for optimization algorithms. By using different weights, the score can also be precisely adjusted to the specific use case. That is why we named it TOMME, which stands for "The One Metric Measuring Errors". As the name suggests, it measures errors in the data. It can thus be considered a generalized, weighted form of accuracy.

cs.DB

Extending GouDa: Generation of Universal Datasets with (and without) Errors for Data Quality Benchmarking

Synthetic data is extremely important in areas such as data quality, data cleaning, and machine learning. It enables the analysis of use cases in which real data is insufficient, unavailable, or distorted. However, generating synthetic data also presents challenges: The data must be as realistic as possible, but at the same time cover edge cases. It must be possible to insert controlled errors, and at the same time, an error-free version of the data is usually required. Additionally, it is necessary to consider numerous data formats, such as tabular data, but also NoSQL data models. To this end, we present our data generator GouDa. GouDa precisely meets these requirements - it is suitable for different data formats, enables the controlled insertion of errors, and generates ground truth. A wide range of different generation functions and the option to add your own lists of possible attribute values allow the generation of realistic data that covers many different use cases.

cs.DB

Solving Distributed Flexible Job Shop Scheduling Problems in the Wool Textile Industry with Quantum Annealing

Many modern manufacturing companies have evolved from a single production facility to a multi-factory production environment that must manage both regionally dispersed production orders and their multi-site production steps. The availability of a range of machines in different locations capable of performing the same operation and shipping times between factories have transformed planning systems from the classic Job Shop Scheduling Problem (JSSP) to the Distributed Flexible Job Shop Scheduling Problem (DFJSP). Consequently, the complexity of production planning has increased significantly. We employ Quantum Annealing (QA) to solve the DFJSP in our research. In addition to assigning production orders to production sites, production steps are also assigned to these sites. This requirement is based on a real use case of a wool textile manufacturing company. To investigate the applicability of this method to large problem instances, problems ranging from 50 variables up to 250 variables, the largest problem that could be embedded into a D-Wave quantum annealer Quantum Processing Unit (QPU), are formulated and solved. Special Attention is dedicated to determining the Lagrange parameters of the Quadratic Unconstrained Binary Optimization (QUBO) model and the QPU configuration parameters, as these factors can significantly impact solution quality. The obtained solutions are compared to solutions obtained by Simulated Annealing (SA), both in terms of solution quality and calculation time. The results demonstrate that QA has the potential to solve large problem instances specific to the industry.

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QC-Adviser: Quantum Hardware Recommendations for Solving Industrial Optimization Problems

The availability of quantum hardware via the cloud offers opportunities for new approaches to computing optimization problems in an industrial environment. However, selecting the right quantum hardware is difficult for non-experts due to its technical characteristics. In this paper, we present the QC-Adviser prototype, which supports users in selecting suitable quantum annealer hardware without requiring quantum computing knowledge.

quant-ph

Towards Next Generation Data Engineering Pipelines

Data engineering pipelines are a widespread way to provide high-quality data for all kinds of data science applications. However, numerous challenges still remain in the composition and operation of such pipelines. Data engineering pipelines do not always deliver high-quality data. By default, they are also not reactive to changes. When new data is coming in which deviates from prior data, the pipeline could crash or output undesired results. We therefore envision three levels of next generation data engineering pipelines: optimized data pipelines, self-aware data pipelines, and self-adapting data pipelines. Pipeline optimization addresses the composition of operators and their parametrization in order to achieve the highest possible data quality. Self-aware data engineering pipelines enable a continuous monitoring of its current state, notifying data engineers on significant changes. Self-adapting data engineering pipelines are then even able to automatically react to those changes. We propose approaches to achieve each of these levels.

cs.DB

MVIAnalyzer: A Holistic Approach to Analyze Missing Value Imputation

Missing values often limit the usage of data analysis or cause falsification of results. Therefore, methods of missing value imputation (MVI) are of great significance. However, in general, there is no universal, fair MVI method for different tasks. This work thus places MVI in the overall context of data analysis. For this purpose, we present the MVIAnalyzer, a generic framework for a holistic analysis of MVI. It considers the overall process up to the application and analysis of machine learning methods. The associated software is provided and can be used by other researchers for their own analyses. To this end, it further includes a missing value simulation with consideration of relevant parameters. The application of the MVIAnalyzer is demonstrated on data with different characteristics. An evaluation of the results shows the possibilities and limitations of different MVI methods. Since MVI is a very complex topic with different influencing variables, this paper additionally illustrates how the analysis can be supported by visualizations.

cs.DB

Data Cleaning of Data Streams

Streaming data can arise from a variety of contexts. Important use cases are continuous sensor measurements such as temperature, light or radiation values. In the process, streaming data may also contain data errors that should be cleaned before further use. Many studies from science and practice focus on data cleaning in a static context. However, in terms of data cleaning, streaming data has particularities that distinguish it from static data. In this paper, we have therefore undertaken an intensive exploration of data cleaning of data streams. We provide a detailed analysis of the applicability of data cleaning to data streams. Our theoretical considerations are evaluated in comprehensive experiments. Using a prototype framework, we show that cleaning is not consistent when working with data streams. An additional contribution is the investigation of requirements for streaming technologies in context of data cleaning.

cs.DB

Hybrid Data Management Architecture for Present Quantum Computing

Quantum computers promise polynomial or exponential speed-up in solving certain problems compared to classical computers. However, in practical use, there are currently a number of fundamental technical challenges. One of them concerns the loading of data into quantum computers, since they cannot access common databases. In this vision paper, we develop a hybrid data management architecture in which databases can serve as data sources for quantum algorithms. To test the architecture, we perform experiments in which we assign data points stored in a database to clusters. For cluster assignment, a quantum algorithm processes this data by determining the distances between data points and cluster centroids.

cs.ET

Extracting JSON Schemas with Tagged Unions

With data lakes and schema-free NoSQL document stores, extracting a descriptive schema from JSON data collections is an acute challenge. In this paper, we target the discovery of tagged unions, a JSON Schema design pattern where the value of one property of an object (the tag) conditionally implies subschemas for sibling properties. We formalize these implications as conditional functional dependencies and capture them using the JSON Schema operators if-then-else. We further motivate our heuristics to avoid overfitting. Experiments with our prototype implementation are promising, and show that this form of tagged unions can successfully be detected in real-world GeoJSON and TopoJSON datasets. In discussing future work, we outline how our approach can be extended further.

cs.DB

NoSQL Database Tuning through Machine Learning

NoSQL databases have become an important component of many big data and real-time web applications. Their distributed nature and scalability make them an ideal data storage repository for a variety of use cases. While NoSQL databases are delivered with a default ''off-the-shelf'' configuration, they offer configuration settings to adjust a database's behavior and performance to a specific use case and environment. The abundance and oftentimes imperceptible inter-dependencies of configuration settings make it difficult to optimize and performance-tune a NoSQL system. There is no one-size-fits-all configuration and therefore the workload, the physical design, and available resources need to be taken into account when optimizing the configuration of a NoSQL database. This work explores Machine Learning as a means to automatically tune a NoSQL database for optimal performance. Using Random Forest and Gradient Boosting Decision Tree Machine Learning algorithms, multiple Machine Learning models were fitted with a training dataset that incorporates properties of the NoSQL physical configuration (replication and sharding). The best models were then employed as surrogate models to optimize the Database Management System's configuration settings for throughput and latency using a Black-box Optimization algorithm. Using an Apache Cassandra database, multiple experiments were carried out to demonstrate the feasibility of this approach, even across varying physical configurations. The tuned DBMS configurations yielded throughput improvements of up to 4%, read latency reductions of up to 43%, and write latency reductions of up to 39% when compared to the default configuration settings.

cs.DB

MigCast in Monte Carlo: The Impact of Data Model Evolution in NoSQL Databases

During the development of NoSQL-backed software, the data model evolves naturally alongside the application code. Especially in agile development, new application releases are deployed frequently causing schema changes. Eventually, decisions have to be made regarding the migration of versioned legacy data which is persisted in the cloud-hosted production database. We solve this schema evolution problem and present the results of near-exhaustive calculations by means of which software project stakeholders can manage the operative costs for data model evolution and adapt their software release strategy accordingly in order to comply with service-level agreements regarding the competing metrics of migration costs and latency. We clarify conclusively how data model evolution in NoSQL databases impacts the metrics while taking all relevant characteristics of migration scenarios into account. As calculating all possible combinatorics in the search space of migration scenarios would by far exceed computational means, we used a probabilistic Monte Carlo method of repeated sampling, serving as a well-established means to bring the complexity of data model evolution under control. Our experiments show the qualitative and quantitative impact on the performance of migration strategies with respect to intensity and distribution of data entity accesses, the kinds of schema changes, and the characteristics of the underlying data model.

cs.DB

Managing Schema Evolution in NoSQL Data Stores

NoSQL data stores are commonly schema-less, providing no means for globally defining or managing the schema. While this offers great flexibility in early stages of application development, developers soon can experience the heavy burden of dealing with increasingly heterogeneous data. This paper targets schema evolution for NoSQL data stores, the complex task of adapting and changing the implicit structure of the data stored. We discuss the recommendations of the developer community on handling schema changes, and introduce a simple, declarative schema evolution language. With our language, software developers and architects can systematically manage the evolution of their production data and perform typical schema maintenance tasks. We further provide a holistic NoSQL database programming language to define the semantics of our schema evolution language. Our solution does not require any modifications to the NoSQL data store, treating the data store as a black box. Thus, we want to address application developers that use NoSQL systems

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