Universität Stuttgart
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Item Open Access Composite-object views in relational DBMS: an implementation perspective(1994) Pirahesh, Hamid; Mitschang, Bernhard; Südkamp, Norbert; Lindsay, BruceWe present a novel approach for supporting Composite Objects (CO) as an abstraction over the relational data. This approach brings the advanced CO model to existing relational databases and applications, without requiring an expensive migration to other DBMSs which support CO. The concept of views in relational DBMSs (RDBMS) gives the basis for providing the CO abstraction. This model is strictly an extension to the relational model, and it is fully upward compatible with it. We present an overview of the data model. We put emphasis in this paper on showing how we have made the extensions to the architecture and implementation of an RDBMS (Starburst) to support this model. We show that such a major extension to the data model is in fact quite attractive both in terms of implementation cost and query performance. We introduce a CO cache for navigation through components of a CO. With this technique, the performance of navigation through COs, which has been of a concern in RDBMSs in the past, is in fact quite satisfactory. We present our practical experience in using this facility. We show that our work on CO enables existing RDBMSs to incorporate efficient CO facilities at a low cost and at a high degree of application reusability and database sharability.Item Open Access Struktur und Verwaltung grafischer Daten(1986) Hübel, Christoph; Mitschang, BernhardDie Arbeitsgruppe Datenverwaltungssysteme am Fachbereich Informatik der Universität Kaiserslautern befaßt sich schon seit längerem im Rahmen des Sonderforschungsbereichs "VLSI-Entwurfsstrukturen und Parallelität" mit der Thematik des Datenbankeinsatzes in sogenannten "Nicht-Standard"-Datenbankanwendungen. Seit kurzem werden diese Forschungsaktivitäten noch ergänzt durch das neugeschaffene "Zentrum für Rechnergestützte Ingenieursysteme". Innerhalb dieser Projekte wurden bereits verschiedene datenbankbasierende Software-Prototypen aus den Bereichen VLSI-Entwurf, geografische lnformationssysteme, Expertensysteme und rechnergestützte Konstruktion entwickelt. Dabei trat überall die Problematik der Strukturierung und Verwaltung grafischer Daten zum Vorschein. Dies gab Anlaß zu einer systematischen Untersuchung des Zusammenspiels von Grafik- und Datenbanksystem, deren Ergebnisse in der Folge dargelegt werden.Item Open Access Grand tour of concepts for object-orientation from a database point of view(1993) Mattos, Nelson Mendonca; Meyer-Wegener, Klaus; Mitschang, BernhardOver the last few years, object-orientation has gained more and more importance within several disciplines of computer science (e.g. programming languages, knowledge engineering, and database systems). Numerous papers have defined one or another of its underlying concepts (sometimes in quite different ways), and some systems have been developed following those heterogeneous definitions. Nevertheless, papers investigating the dependencies and degrees of freedom of these concepts are rarely found. For this reason, the goal of this paper is not to add yet another definition of object-oriented concepts, but to identify existing relationships among these basic concepts that allow one to cover and classify various conceivable combinations of these conceptual building blocks. Dependencies, orthogonalities, and relations among concepts like object identity, encapsulation, classification, generalization, inheritance, etc. are revealed, showing numerous ways to compose different shades of object-orientation. This leads to alternatives encountered when constructing object-oriented systems, which are illustrated by classifying some well-known systems and prototypes from different areas. However, it is not our purpose to analyze the relative importance of these concepts. Instead, we investigate the concepts from a neutral point of view, presenting (but not evaluating) several degrees of object-orientation.Item Open Access SMARTEN : a sample-based approach towards privacy-friendly data refinement(2022) Stach, Christoph; Behringer, Michael; Bräcker, Julia; Gritti, Clémentine; Mitschang, BernhardTwo factors are crucial for the effective operation of modern-day smart services: Initially, IoT-enabled technologies have to capture and combine huge amounts of data on data subjects. Then, all these data have to be processed exhaustively by means of techniques from the area of big data analytics. With regard to the latter, thorough data refinement in terms of data cleansing and data transformation is the decisive cornerstone. Studies show that data refinement reaches its full potential only by involving domain experts in the process. However, this means that these experts need full insight into the data in order to be able to identify and resolve any issues therein, e.g., by correcting or removing inaccurate, incorrect, or irrelevant data records. In particular for sensitive data (e.g., private data or confidential data), this poses a problem, since these data are thereby disclosed to third parties such as domain experts. To this end, we introduce SMARTEN, a sample-based approach towards privacy-friendly data refinement to smarten up big data analytics and smart services. SMARTEN applies a revised data refinement process that fully involves domain experts in data pre-processing but does not expose any sensitive data to them or any other third-party. To achieve this, domain experts obtain a representative sample of the entire data set that meets all privacy policies and confidentiality guidelines. Based on this sample, domain experts define data cleaning and transformation steps. Subsequently, these steps are converted into executable data refinement rules and applied to the entire data set. Domain experts can request further samples and define further rules until the data quality required for the intended use case is reached. Evaluation results confirm that our approach is effective in terms of both data quality and data privacy.Item Metadata only Processing and transaction concepts for cooperation of engineering workstations and a database server(1988) Härder, Theo; Hübel, Christoph; Meyer-Wegener, Klaus; Mitschang, BernhardA DBMS kernel architecture is proposed for improved DB support of engineering applications running on a cluster of workstations. Using such an approach, part of the DBMS code - an application-specific layer - is allocated close to the corresponding application on a workstation while the kernel code is executed on a central server. Emperical performance results from DB-based engineering applications are reported to justify the chosen DBMS architecture. The paper focuses on design issues of the application layer including server coupling, processing model and application interface. Moreover, a transaction model for long-term database work in a coupled workstation-server environment is investigated in detail.Item Open Access KUNICAD : ein datenbankgestütztes geometrisches Modellierungssystem für Werkstücke(1987) Härder, Theo; Hübel, Christoph; Langenfeld, Stefan; Mitschang, BernhardEs wird ein datenbankgestütztes, volumenorientiertes Modellierungssystem für Werkstücke beschrieben, das als Kernalgorithmus für die geometrische Modellierung ein volumenorientiertes Verfahren einsetzt. Zur Unterstützung der graphischen Repräsentation der Werkstücke werden intern zusätzlich Strukturen nach dem Begrenzungsflächenmodell gehalten, die automatisch aus den CSG-Strukturen abgeleitet und nachgeführt werden. Das KUNICAD-System wird durch seine Gesamtarchitektur, seine Benutzerschnittstelle und sein zugrundeliegendes Anwendermodell skizziert. Die Modellierungskomponente wird durch ihre wesentlichsten Aufgaben - die Darstellung der Objekte und ihre Handhabung - beschrieben. Eine objektunterstützende Datenbankschnittstelle wurde nach dem Zusatzebenen-Architekturkonzept auf der Basis eines CODASYL-Datenbanksystems (UDS) entwickelt. Das implementierte System gestattet das Studium von praxistauglichen CAD-Schnittstellen und erlaubt eine detaillierte Analyse des durch die Datenbankverwaltung bedingten Mehraufwands bei CAD-Operationen.Item Open Access DB-Schnittstellen für arbeitsplatzorientierte Ingenieuranwendungen(1988) Hübel, Christoph; Mitschang, BernhardDie Schnittstellen gegenwärtig verfügbarer Datenbanksysteme erweisen sich als ungeeignet für den Bereich der lngenieuranwendungen. Dies gilt im besonderen, da bei Ingenieuranwendungen eine deutliche Arbeitsplatzorientierung vorherrscht und sie damit häufig auf einer speziellen Mehrrechnerarchitektur aufbauen. Ausgehend von einem Schichtenmodell für sog. Non-Standard-Datenbanksysteme (NDBS) schlagen wir daher eine spezielle Systemarchitektur mit einer entsprechend ausgelegten Datenmodell- und Anwendungsmodellschnittstelle für arbeitsplatzorientierte Ingenieuranwendungen vor.Item Open Access Query processing in blockchain systems : current state and future challenges(2021) Przytarski, Dennis; Stach, Christoph; Gritti, Clémentine; Mitschang, BernhardWhen, in 2008, Satoshi Nakamoto envisioned the first distributed database management system that relied on cryptographically secured chain of blocks to store data in an immutable and tamper-resistant manner, his primary use case was the introduction of a digital currency. Owing to this use case, the blockchain system was geared towards efficient storage of data, whereas the processing of complex queries, such as provenance analyses of data history, is out of focus. The increasing use of Internet of Things technologies and the resulting digitization in many domains, however, have led to a plethora of novel use cases for a secure digital ledger. For instance, in the healthcare sector, blockchain systems are used for the secure storage and sharing of electronic health records, while the food industry applies such systems to enable a reliable food-chain traceability, e.g., to prove compliance with cold chains. In these application domains, however, querying the current state is not sufficient - comprehensive history queries are required instead. Due to these altered usage modes involving more complex query types, it is questionable whether today’s blockchain systems are prepared for this type of usage and whether such queries can be processed efficiently by them. In our paper, we therefore investigate novel use cases for blockchain systems and elicit their requirements towards a data store in terms of query capabilities. We reflect the state of the art in terms of query support in blockchain systems and assess whether it is capable of meeting the requirements of such more sophisticated use cases. As a result, we identify future research challenges with regard to query processing in blockchain systems.Item Open Access Protecting sensitive data in the information age : state of the art and future prospects(2022) Stach, Christoph; Gritti, Clémentine; Bräcker, Julia; Behringer, Michael; Mitschang, BernhardThe present information age is characterized by an ever-increasing digitalization. Smart devices quantify our entire lives. These collected data provide the foundation for data-driven services called smart services. They are able to adapt to a given context and thus tailor their functionalities to the user’s needs. It is therefore not surprising that their main resource, namely data, is nowadays a valuable commodity that can also be traded. However, this trend does not only have positive sides, as the gathered data reveal a lot of information about various data subjects. To prevent uncontrolled insights into private or confidential matters, data protection laws restrict the processing of sensitive data. One key factor in this regard is user-friendly privacy mechanisms. In this paper, we therefore assess current state-of-the-art privacy mechanisms. To this end, we initially identify forms of data processing applied by smart services. We then discuss privacy mechanisms suited for these use cases. Our findings reveal that current state-of-the-art privacy mechanisms provide good protection in principle, but there is no compelling one-size-fits-all privacy approach. This leads to further questions regarding the practicality of these mechanisms, which we present in the form of seven thought-provoking propositions.Item Open Access AssistML : an approach to manage, recommend and reuse ML solutions(2023) Villanueva Zacarias, Alejandro Gabriel; Reimann, Peter; Weber, Christian; Mitschang, BernhardThe adoption of machine learning (ML) in organizations is characterized by the use of multiple ML software components. When building ML systems out of these software components, citizen data scientists face practical requirements which go beyond the known challenges of ML, e. g., data engineering or parameter optimization. They are expected to quickly identify ML system options that strike a suitable trade-off across multiple performance criteria. These options also need to be understandable for non-technical users. Addressing these practical requirements represents a problem for citizen data scientists with limited ML experience. This calls for a concept to help them identify suitable ML software combinations. Related work, e. g., AutoML systems, are not responsive enough or cannot balance different performance criteria. This paper explains how AssistML, a novel concept to recommend ML solutions, i. e., software systems with ML models, can be used as an alternative for predictive use cases. Our concept collects and preprocesses metadata of existing ML solutions to quickly identify the ML solutions that can be reused in a new use case. We implement AssistML and evaluate it with two exemplary use cases. Results show that AssistML can recommend ML solutions in line with users’ performance preferences in seconds. Compared to AutoML, AssistML offers citizen data scientists simpler, intuitively explained ML solutions in considerably less time. Moreover, these solutions perform similarly or even better than AutoML models.