Die Arbeit diskutiert Lösungsvarianten und beschreibt die Implementation eines Prototyps zur Re-Organisation der Nutzerverwaltung des URZ. Besondere Schwerpunkte liegen auf der Erstellung eines Web-Interfaces zur Datenverwaltung und auf der Untersuchung relationaler Datenbanksysteme hinsichtlich der Eignung zur Lösung der Aufgabe. Der Prototyp stellt lediglich eine beispielhafte Implementierung einiger Teilkomplexe des Gesamtsystems dar.

We present an axiomatization of relational varieties, i.e., classes of relational structures closed under formation of products and retracts, by a certain class of first-order sentences. We apply this result to categorically equivalent algebras and primal algebras. We consider the relational varieties generated by structures with minimal clone, rigid structures and two-element structures.

Software developers adapt to the fast-moving nature of software systems with agile development techniques. However, database developers lack the tools and concepts to keep the pace. Whenever the current database schema is evolved, the already existing data needs to be evolved as well. This is usually realized with manually written SQL scripts, which is error-prone and explains significant costs in software projects. A promising solution are declarative database evolution languages, which couple both schema and data evolution into intuitive operations. Existing database evolution languages focus on usability but do not strive for completeness. However, this is an inevitable prerequisite to avoid complex and error-prone workarounds. We present CODEL which is based on an existing language but is relationally complete. We precisely define its semantic using relational algebra, propose a syntax, and formally validate its relational completeness. Having a complete and comprehensive database evolution language facilitates valuable support throughout the whole evolution of a database. As an instance, we present VACO, a tool supporting developers with variant co-evolution. Given a variant schema derived from a core schema, VACO uses the richer semantics of CODEL to semi-automatically co-evolve this variant with the core.

Relational database management systems build on the closed world assumption requiring upfront modeling of a usually stable schema. However, a growing number of today's database applications are characterized by self-descriptive data. The schema of self-descriptive data is very dynamic and prone to frequent changes; a situation which is always troublesome to handle in relational systems. This demo presents the relational database management system FRDM. With flexible relational tables FRDM greatly simplifies the management of self-descriptive data in a relational database system. Self-descriptive data can reside directly next to traditionally modeled data and both can be queried together using SQL. This demo presents the various features of FRDM and provides first-hand experience of the newly gained freedom in relational database systems.

This thesis extends a localisation theory for finite algebras to certain classes of infinite structures. Based on ideas and constructions originally stemming from Tame Congruence Theory, algebras are studied via local restrictions of their relational counterpart (Relational Structure Theory). In this respect, first those subsets are identified that are suitable for such a localisation process, i. e. that are compatible with the relational clone structure of the counterpart of an algebra. It is then studied which properties of the global algebra can be transferred to its localisations, called neighbourhoods. Thereafter, it is discussed how this process can be reversed, leading to the concept of covers. These are collections of neighbourhoods that allow information retrieval about the global structure from knowledge about the local restrictions. Subsequently, covers are characterised in terms of a decomposition equation, and connections to categorical equivalences of algebras are explored. In the second half of the thesis, a refinement concept for covers is introduced in order to find optimal, non-refinable covers, eventually leading to practical algorithms for their determination. Finally, the text establishes further theoretical foundations, e. g. several irreducibility notions, in order to ensure existence of non-refinable covers via an intrinsic characterisation, and to prove under some conditions that they are uniquely determined in a canonical sense. At last, the applicability of the developed techniques is demonstrated using two clear expository examples. / Diese Dissertation erweitert eine Lokalisierungstheorie für endliche Algebren auf gewisse Klassen unendlicher Strukturen. Basierend auf Ideen und Konstruktionen, die ursprünglich der Tame Congruence Theory entstammen, werden Algebren über lokale Einschränkungen ihres relationalen Gegenstücks untersucht (Relationale Strukturtheorie). In diesem Zusammenhang werden zunächst diejenigen Teilmengen identifiziert, welche für einen solchen Lokalisierungsprozeß geeignet sind, d. h., die mit der Relationenklonstruktur auf dem Gegenstück einer Algebra kompatibel sind. Es wird dann untersucht, welche Eigenschaften der globalen Algebra auf ihre Lokalisierungen, genannt Umgebungen, übertragen werden können. Nachfolgend wird diskutiert, wie dieser Vorgang umgekehrt werden kann, was zum Begriff der Überdeckungen führt. Dies sind Systeme von Umgebungen, welche die Rückgewinnung von Informationen über die globale Struktur aus Kenntnis ihrer lokalen Einschränkungen erlauben. Sodann werden Überdeckungen durch eine Zerlegungsgleichung charakterisiert und Bezüge zu kategoriellen Äquivalenzen von Algebren hergestellt. In der zweiten Hälfte der Arbeit wird ein Verfeinerungsbegriff für Überdeckungen eingeführt, um optimale, nichtverfeinerbare Überdeckungen zu finden, was letztlich zu praktischen Algorithmen zu ihrer Bestimmung führt. Schließlich erarbeitet der Text weitere theoretische Grundlagen, beispielsweise mehrere Irreduzibilitätsbegriffe, um die Existenz nichtverfeinerbarer Überdeckungen vermöge einer intrinsischen Charakterisierung sicherzustellen und, unter gewissen Bedingungen, zu beweisen, daß sie in kanonischer Weise eindeutig bestimmt sind. Schlußendlich wird die Anwendbarkeit der entwickelten Methoden an zwei übersichtlichen Beispielen demonstriert.

This thesis extends a localisation theory for finite algebras to certain classes of infinite structures. Based on ideas and constructions originally stemming from Tame Congruence Theory, algebras are studied via local restrictions of their relational counterpart (Relational Structure Theory). In this respect, first those subsets are identified that are suitable for such a localisation process, i. e. that are compatible with the relational clone structure of the counterpart of an algebra. It is then studied which properties of the global algebra can be transferred to its localisations, called neighbourhoods. Thereafter, it is discussed how this process can be reversed, leading to the concept of covers. These are collections of neighbourhoods that allow information retrieval about the global structure from knowledge about the local restrictions. Subsequently, covers are characterised in terms of a decomposition equation, and connections to categorical equivalences of algebras are explored. In the second half of the thesis, a refinement concept for covers is introduced in order to find optimal, non-refinable covers, eventually leading to practical algorithms for their determination. Finally, the text establishes further theoretical foundations, e. g. several irreducibility notions, in order to ensure existence of non-refinable covers via an intrinsic characterisation, and to prove under some conditions that they are uniquely determined in a canonical sense. At last, the applicability of the developed techniques is demonstrated using two clear expository examples.:1 Introduction 2 Preliminaries and Notation 2.1 Functions, operations and relations 2.2 Algebras and relational structures 2.3 Clones 3 Relational Structure Theory 3.1 Finding suitable subsets for localisation 3.2 Neighbourhoods 3.3 The restricted algebra A|U 3.4 Covers 3.5 Refinement 3.6 Irreducibility notions 3.7 Intrinsic description of non-refinable covers 3.8 Elaborated example 4 Problems and Prospects for Future Research Acknowledgements Index of Notation Index of Terms Bibliography / Diese Dissertation erweitert eine Lokalisierungstheorie für endliche Algebren auf gewisse Klassen unendlicher Strukturen. Basierend auf Ideen und Konstruktionen, die ursprünglich der Tame Congruence Theory entstammen, werden Algebren über lokale Einschränkungen ihres relationalen Gegenstücks untersucht (Relationale Strukturtheorie). In diesem Zusammenhang werden zunächst diejenigen Teilmengen identifiziert, welche für einen solchen Lokalisierungsprozeß geeignet sind, d. h., die mit der Relationenklonstruktur auf dem Gegenstück einer Algebra kompatibel sind. Es wird dann untersucht, welche Eigenschaften der globalen Algebra auf ihre Lokalisierungen, genannt Umgebungen, übertragen werden können. Nachfolgend wird diskutiert, wie dieser Vorgang umgekehrt werden kann, was zum Begriff der Überdeckungen führt. Dies sind Systeme von Umgebungen, welche die Rückgewinnung von Informationen über die globale Struktur aus Kenntnis ihrer lokalen Einschränkungen erlauben. Sodann werden Überdeckungen durch eine Zerlegungsgleichung charakterisiert und Bezüge zu kategoriellen Äquivalenzen von Algebren hergestellt. In der zweiten Hälfte der Arbeit wird ein Verfeinerungsbegriff für Überdeckungen eingeführt, um optimale, nichtverfeinerbare Überdeckungen zu finden, was letztlich zu praktischen Algorithmen zu ihrer Bestimmung führt. Schließlich erarbeitet der Text weitere theoretische Grundlagen, beispielsweise mehrere Irreduzibilitätsbegriffe, um die Existenz nichtverfeinerbarer Überdeckungen vermöge einer intrinsischen Charakterisierung sicherzustellen und, unter gewissen Bedingungen, zu beweisen, daß sie in kanonischer Weise eindeutig bestimmt sind. Schlußendlich wird die Anwendbarkeit der entwickelten Methoden an zwei übersichtlichen Beispielen demonstriert.:1 Introduction 2 Preliminaries and Notation 2.1 Functions, operations and relations 2.2 Algebras and relational structures 2.3 Clones 3 Relational Structure Theory 3.1 Finding suitable subsets for localisation 3.2 Neighbourhoods 3.3 The restricted algebra A|U 3.4 Covers 3.5 Refinement 3.6 Irreducibility notions 3.7 Intrinsic description of non-refinable covers 3.8 Elaborated example 4 Problems and Prospects for Future Research Acknowledgements Index of Notation Index of Terms Bibliography

Diese Dissertation enthält drei Aufsätze zur Theorie der Anreizsetzung bei nicht-verifizierbaren Leistungsmaßen. Untersuchungsgegenstand sind die Auswirkungen individueller Fairnesspräferenzen auf die Ausgestaltung und Eignung verschiedener Anreizmechanismen, welche in realen wirtschaftlichen Situationen Anwendung finden. Alle Arbeiten analysieren Umgebungen moralischen Risikos, in denen eine Firma zwei ungerechtigkeitsaverse Mitarbeiter beschäftigt, deren individuelle Arbeitsleistung zwar beobachtbar, jedoch nicht kontrahierbar ist. Der erste Aufsatz untersucht die Effekte von Ungerechtigkeitsaversion auf relationale Anreizverträge. Als Leistungsmaß eines Agenten dient sein individueller Beitrag zum Firmenwert. Abweichend von der Literatur zeigt sich, dass Ungerechtigkeitsaversion vorteilhaft sein kann: Für bestimmte Zinssätze können relationale Verträge mit neidischen Agenten profitabler sein, wenn sie nicht sogar nur mit solchen implementierbar sind. Der zweite Aufsatz vergleicht relationale Individual- und Gruppenbonusverträge. Durch das Vermeiden ungleicher Löhne sind letztere profitabler, solange sich die Firma keinem Glaubwürdigkeitsproblem gegenübersieht. Dies kann sich jedoch umkehren, da Individualboni vergleichsweise kleiner sind und somit die Selbstdurchsetzung des Vertrags fördern. Ursachen dafür sind das Vermeiden des Trittbrettfahrerproblems und die Anreizwirkung von Neid. Im dritten Aufsatz wird relationalen Individualbonusverträgen ein relatives Leistungsturnier gegenübergestellt. Im Gegensatz zum Bonusvertrag unterliegt das Turnier keiner Glaubwürdigkeitsbeschränkung. Dennoch ist ersteres Anreizschema profitabler, solange das Glaubwürdigkeitsproblem der Firma nicht zu groß ist. Dies liegt an der zwingenden Auszahlung ungleicher Löhne im Turnier und den daraus resultierenden hohen Kosten für Ungleichheitsprämien. Weiter wird für ein Beispiel gezeigt, dass die Zinsspanne, für die der Bonusvertrag das Turnier dominiert, im Neid der Agenten steigt. / This thesis consists of three self-contained essays that investigate the impact of fairness concerns among agents on the design of real-world incentive contracts used to mitigate moral-hazard problems under non-verifiable performance. All papers consider situations in which a firm employs two inequity averse workers whose individual performances are, albeit observable by the contracting parties, not contractible. The first paper studies the effects of inequity aversion on relational employment contracts. Performance is evaluated via an agent’s individual non-verifiable contribution to firm value. In contrast to the literature, we find that inequity aversion may be beneficial: In the presence of envy, for a certain range of interest rates relational contracts may be more profitable. For some interest rates reputational equilibria exist only with envious agents. In the second paper, I compare group to individual performance pay. Avoiding payoff inequity, the group bonus contract is superior as long as the firm faces no credibility problem. The individual bonus contract may, however, become superior due to two reasons: The group bonus scheme is subject to a free-rider problem requiring a higher incentive pay and impeding credibility of the firm. Moreover, with individual bonuses the firm benefits from the incentive-strengthening effect of envy, further softening the credibility constraint. The third paper contrasts a rank-order tournament with independent bonus contracts. Whereas the bonus scheme must be self-enforcing, the tournament is contractible. Yet the former incentive regime outperforms the latter as long as credibility problems are not too severe. This is due the fact that the tournament requires unequal pay across peers with certainty and thus imposes large inequity premium costs on the firm. For a simple example, I show that the more envious the agents are the larger is the range of interest rates for which the bonus scheme dominates the tournament.

With the ongoing expansion of information technology, new fields of application requiring data management emerge virtually every day. In our knowledge culture increasing amounts of data and work force organized in more creativity-oriented ways also radically change traditional fields of application and question established assumptions about data management. For instance, investigative analytics and agile software development move towards a very agile and flexible handling of data. As the primary facilitators of data management, database systems have to reflect and support these developments. However, traditional database management technology, in particular relational database systems, is built on assumptions of relatively stable application domains. The need to model all data up front in a prescriptive database schema earned relational database management systems the reputation among developers of being inflexible, dated, and cumbersome to work with. Nevertheless, relational systems still dominate the database market. They are a proven, standardized, and interoperable technology, well-known in IT departments with a work force of experienced and trained developers and administrators. This thesis aims at resolving the growing contradiction between the popularity and omnipresence of relational systems in companies and their increasingly bad reputation among developers. It adapts relational database technology towards more agility and flexibility. We envision a descriptive schema-comes-second relational database system, which is entity-oriented instead of schema-oriented; descriptive rather than prescriptive. The thesis provides four main contributions: (1)~a flexible relational data model, which frees relational data management from having a prescriptive schema; (2)~autonomous physical entity domains, which partition self-descriptive data according to their schema properties for better query performance; (3)~a freely adjustable storage engine, which allows adapting the physical data layout used to properties of the data and of the workload; and (4)~a self-managed indexing infrastructure, which autonomously collects and adapts index information under the presence of dynamic workloads and evolving schemas. The flexible relational data model is the thesis\' central contribution. It describes the functional appearance of the descriptive schema-comes-second relational database system. The other three contributions improve components in the architecture of database management systems to increase the query performance and the manageability of descriptive schema-comes-second relational database systems. We are confident that these four contributions can help paving the way to a more flexible future for relational database management technology.

With the ongoing expansion of information technology, new fields of application requiring data management emerge virtually every day. In our knowledge culture increasing amounts of data and work force organized in more creativity-oriented ways also radically change traditional fields of application and question established assumptions about data management. For instance, investigative analytics and agile software development move towards a very agile and flexible handling of data. As the primary facilitators of data management, database systems have to reflect and support these developments. However, traditional database management technology, in particular relational database systems, is built on assumptions of relatively stable application domains. The need to model all data up front in a prescriptive database schema earned relational database management systems the reputation among developers of being inflexible, dated, and cumbersome to work with. Nevertheless, relational systems still dominate the database market. They are a proven, standardized, and interoperable technology, well-known in IT departments with a work force of experienced and trained developers and administrators. This thesis aims at resolving the growing contradiction between the popularity and omnipresence of relational systems in companies and their increasingly bad reputation among developers. It adapts relational database technology towards more agility and flexibility. We envision a descriptive schema-comes-second relational database system, which is entity-oriented instead of schema-oriented; descriptive rather than prescriptive. The thesis provides four main contributions: (1)~a flexible relational data model, which frees relational data management from having a prescriptive schema; (2)~autonomous physical entity domains, which partition self-descriptive data according to their schema properties for better query performance; (3)~a freely adjustable storage engine, which allows adapting the physical data layout used to properties of the data and of the workload; and (4)~a self-managed indexing infrastructure, which autonomously collects and adapts index information under the presence of dynamic workloads and evolving schemas. The flexible relational data model is the thesis\' central contribution. It describes the functional appearance of the descriptive schema-comes-second relational database system. The other three contributions improve components in the architecture of database management systems to increase the query performance and the manageability of descriptive schema-comes-second relational database systems. We are confident that these four contributions can help paving the way to a more flexible future for relational database management technology.

The progress in genome research demands for an adequate infrastructure to analyze the data sets. Database systems reflect a key technology to organize data and speed up the analysis process. This paper discusses the role of a relational database system based on the problem of finding frequent substructures in multi-dimensional protein databases. The specific problem consists of producing a set of association rules regarding frequent substructures with different lengths and gaps between the amino acid residues of a protein. From a database point of view, the process of finding association rules building the base for a more in-depth analysis of the data material is split into two parts. The first part performs a discretization of the conformational angle space of a single amino acid residue by computing the nearest neighbor of a given set of representatives. The second part consists in adapting a well-known association rule algorithm to determine the frequent substructures. Both steps within this comprehensive analysis task requires substantial support of the underlying database in order to reduce the programming overhead at the application level.