Contributions published at Database Technology (Michael Hanspeter Böhlen)

A common phenomenon of time-qualified data are temporal repetitions, i.e., the association of multiple time values with the same data. In order to deal with finite and infinite temporal repetitions in databases we must use compact representations. There have been many compact representations proposed, however, not all of them are equally efficient for query evaluation. In order to show it, we define a class of simple queries on compact representations. We compare a query evaluation time on our proposed multi-granular compact representation GSequences with a query evaluation time on single-granular compact representation PSets, based on periodical sets. We show experimentally how the performance of query evaluation can benefit from the compactness of a representation and from a special structure of GSequences.

TeNDaX is a collaborative database-based real-time editor system. TeNDaX is a new approach for word-processing in which documents (i.e. content and structure, tables, images etc.) are stored in a database in a semi-structured way. This supports the provision of collaborative editing and layout, undo- and redo operations, business process definition and execution within documents, security, and awareness. During document creation process and use meta data is gathered automatically. This meta data can then be used for the TeNDaX dynamic folders, data lineage, visual- and text mining and search. We present TeNDaX as a word-processing ‘LAN-Party’: collaborative editing and layout; business process definition and execution; local and global undo- and redo operations; all based on the use of multiple editors and different operating systems. In a second step we demonstrate how one can use the data and meta data to create dynamic folders, visualize data provenance, carry out visual- and text mining and support sophisticated search functionality.

Business Intelligence solutions, encompassing technologies such as multi-dimensional data modeling and aggregate query processing, are being applied increasingly to non-traditional data. This paper extends multi-dimensional aggregation to apply to data with associated interval values that capture when the data hold. In temporal databases, intervals typically capture the states of reality that the data apply to, or capture when the data are, or were, part of the current database state.This paper proposes a new aggregation operator that addresses several challenges posed by interval data. First, the intervals to be associated with the result tuples may not be known in advance, but depend on the actual data. Such unknown intervals are accommodated by allowing result groups that are specified only partially. Second, the operator contends with the case where an interval associated with data expresses that the data holds for each point in the interval, as well as the case where the data holds only for the entire interval, but must be adjusted to apply to sub-intervals. The paper reports on an implementation of the new operator and on an empirical study that indicates that the operator scales to large data sets and is competitive with respect to other temporal aggregation algorithms.

Ontologies are increasingly used to represent the intended real-world semantics of data and services in information systems. Unfortunately, different databases often do not relate to the same ontologies when describing their semantics. Consequently, it is desirable to have information about the similarity between ontology concepts for ontology alignment and integration. This paper presents the SOQA-SimPack Toolkit (SST), an ontology language independent Java API that enables generic similarity detection and visualization in ontologies. We demonstrate SST's usefulness with the SOQA-SimPack Toolkit Browser, which allows users to graphically perform similarity calculations in ontologies.

Most real-world database applications manage temporal data, i.e., data with associated time references that capture a temporal aspect of the data, typically either when the data is valid or when the data is known. Such applications abound in, e.g., the financial, medical, and scientific domains. In contrast to this, current database management systems offer preciously little built-in query language support for temporal data management. This situation persists although an active temporal database research community has demonstrated that application development can be simplified substantially by built-in temporal support. This paper's contribution is motivated by the observation that existing temporal data models and query languages generally make the same rigid assumption about the semantics of the association of data and time, namely that if a subset of the time domain is associated with some data then this implies the association of any further subset with the data. This paper offers a comprehensive, general framework where alternative semantics may co-exist. It supports so-called malleable and atomic temporal associations, in addition to the conventional ones mentioned above, which are termed constant. To demonstrate the utility of the framework, the paper defines a characteristics-enabled temporal algebra, termed CETA, which defines the traditional relational operators in the new framework. This contribution demonstrates that it is possible to provide built-in temporal support while making less rigid assumptions about the data and without jeopardizing the degree of the support. This moves temporal support closer to practical applications.

Organisations in healthcare tend to have many complex requirements for a Workflow Management System. Because of the heterogeneous and dynamic structure of a hospital it is difficult to adequately automate their business processes, of which most are ad hoc and loosely coupled. This thesis starts by outlining the theoretical background and provides a definition for relevant terms of workflow management. Thereupon, several possible WFMS architectures are discussed in the context of a problem scenario. The applicability in a medical environment is analysed for each of these architectures. Based on this research, a WFMS architecture is proposed, which satisfies the healthcare scenario requirements. The most appropriate solution to this scenario is a service-oriented architecture, which is explained in detail.

In this diploma thesis the usability of TeNDaX was analyzed and suggestions for improvements are given. A usable system supports the users in accomplishing their tasks efficiently, effectively and satisfactorily which is a key requirement for a system to be utilized successfully to its full potential. In order to identify usability problems, a usability test with several volunteers was carried out and analyzed. Other hindrances from using a system are inhibitions which may occur in TeNDaX due to the transparency of the text editing process and the storage of all text data, including metadata. A survey with potential users was conducted to ascertain their perception to it and changes for alleviation of inherent setbacks and problems are suggested.

Caused by the technological progress over the last decades and the permanent increase of the global interconnectedness, today we are faced with much more information that we are able to perceive and to handle. Instead of being spported by the information technology this information overload may overhelm a user and impair its productivity. In the context of this thesis new methods are developed for determining representative records from a given dataset. These records help a user in getting an idea of the characteristics of the underlying dataset without having to examine all the data. In this thesis three different approaches for determining representative records will be proposed. Two of them are based on clustering algorithms. The last methed uses the Apriori algorithm in order to find large itemsets in the given data for deriving representative records. The presented methods have been validated against existing datasets. For this purpose a Java based tool was written that implements the proposed algorithms.

The Extensible Markup Language (XML) started as a hype of an all-round technology, but since then it has become a widely used basis for electronic data exchange (e.g. Web Services). After all, well-formed XML documents have always played an important role and are still growing in diversity and size. The question is how to store and manage XML documents efficiently. XML databases promise to offer the right answer. However, as the products available on the market are very diverse, it is not easy to choose the right product. There are many different storage approaches in XML databases, the principles of which a priori are not clear, nor are their differences. This diploma thesis explains those different storage approaches, categorizes the products on the market based on that framework, and evaluates a close-pitch selection using functional requirements and performance tests among other aspects.

Eclipse always was more than just a development environment. It’s also a Java-based and extensible platform for graphical applications. Next to its own numerous features strongly focuses on making the integration of external tools easy. The plugin-concept decisive role. With version 3.0 the use of the Eclipse platform as a universal applicationframework is declared as the main strategy of the Eclipse community. This represented by the Rich Client Platform (RCP) architecture. This diploma thesis working out a clean basis for porting TeNDaX onto the Eclipse platform. This work build the fundament for a professional and solidly structured version of TeNDaX.

The research project TeNDaX deals with the collaborative editing of text documents. The software prototype that results of the attempts to achieve the main goals contains various functionalities. But before it can be used in everyday life, some additional extensions are needed. So far the text processing can only be done with a text editor specially developed for this purpose. However the use of a common Office Suite would be preferable. OpenOffice.org belongs to these widespread software solutions. Besides of the free availability it has due to an open source the advantage of being expandable. Endorsing an existing analysis of integration concepts the present thesis discusses a concrete integration of TeNDaX in OpenOffice.org. It focuses on overcoming the differences between both document models. It can be shown, that the main problem cannot be solved by programming an external component without an adaptation of the source code. Based on this knowledge propositions for an implementation are worked out, progressively extending and adapting both document models up to a complete integration.

While using Extraction, Transformation and Load procedures (ETL) to integrate large amounts of data, performance plays an important role. This performance is influenced by many variables related to the system’s architecture, software design and the underlying hardware environment. This thesis introduces the scientific research areas in and around the optimisation of Data Warehousing (DWH) and ETL and analyses their most significant optimisation frameworks including XML. Furthermore the thesis uses the qualitative evaluation of a number of established commercial data integration solutions as a basis for the assessment and recommendation of the optimal ETL middleware for IBM Business Consulting Service's OASI integration project at the Vontobel bank in Zurich. Thereupon the OASI system is specified, designed, implemented and systematically optimised in order to integrate and improve the daily and intraday processing of the master data into the bank’s portfolio and order management systems. Finally the implemented optimisation recommendations are validated by a number of performance tests which create a new benchmark for OASI’s future development and the optimisation of ETL procedures for the integration of financial data in data warehouse applications.

Content Management Systems (CMS) are already widely used for the management of complex websites. They allow a clear allocation and separation of different tasks within the Content Management (CM) process for specialised individuals. In contrast to websites built of static HTML files, CMS separate content from structure and presentation and allow, therefore, dynamic publications of information. Further, they provide functionalities for supporting the CM process. With the continuous progression of internet technologies and their influence on society, new applications emerged. Unlike traditional CMS, they allow new kinds of interaction between the publisher and visitors. These technologies have been found applicable for Knowledge Management (KM) activities. This diploma thesis evaluates several CMS with regard to their application within KMS.

Measurements at different time points and positions in large temporal or spatial databases requires effective and efficient data mining techniques. For several parallel measurements, finding clusters of arbitrary length and number of attributes, poses additional challenges. We present a novel algorithm capable of finding parallel clusters in different structural quality parameter values for river sequences used by hydrologists to develop measures for river quality improvements.

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Most medical, biological and social studies face the problem of storing information about subjects for research purposes without violating the subject's privacy. In most cases it is not possible to remove all information that could be linked to a subject, because some of this information is needed for the research itself. This fact holds especially for longitudinal studies, which collect data about a subject at different times and places. Longitudinal studies need to link different data about a specific subject, collected at different times for research and administration use. In this paper we present the security concept proposed for sesam, a longitudinal interdisciplinary study that analyses the social, biological and psychological risk factors for the development of psychological diseases. Our security concept is based on pseudonymisation, encrypted data transfer and an electronic data custodianship. This paper is mainly a case study and some of the security problems emerged in the context of sesam may not occur in other studies. Nevertheless we believe that an adopted version of our approach could be used in other application scenarios as well.

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