Data warehouses are used to store large amounts of data. This data is often used for On-Line Analytical Processing (OLAP) where short response times are essential for on-line decision support. One of the most important requirements of a data warehouse server is the query performance. The principal aspect from the user perspective is how quickly the server processes a given query: “the data warehouse must be fast”. The main focus of our research is finding adequate solutions to improve query response time of typical OLAP queries and improve scalability using a distributed computation environment that takes advantage of characteristics specific to the OLAP context. Our proposal provides very good performance and scalability even on huge data warehouses.Weniger anzeigen
The objective of this work is to develop a design methodology for data warehouses. It is based on the three level modeling approach with emphasis on conceptual modeling. Logical design to the relational model and physical tuning in this environment will also be treated.
The Asgaard project stresses the issue of time-oriented, skeletal planning, primarily in the medical domain. We try to support therapy planning by adding computer-aided quality assessment, plan validation and other high-level tasks to the field of planning in real-world environment. Key component is a descriptive plan representation language, called Asbru to enable the acquisition of computer readable medical guidelines. The research question of the Ph.D. student thesis is to prove a basic assumption of the project, that the use of Asbru and computer support is helpful in a real-world, time- oriented planning situation. The idea behind is to connect scientific concepts to the intended real-world target environment. A comparison with the usefulness of related modeling techniques, like workflow-process modeling, will be performed.Weniger anzeigen
The estimation of information value will be a key issue for upcoming intelligent information systems, that not only provide information on request but deal with time-dependently varying information needs. Due to its subjective nature, information value cannot be computed and each individual has a different perception of what exactly is relevant to him. However, we propose a concept of information value and a computational model for its estimation. Our model is based upon the observation that information concerning the future can easily be divided into relevant and irrelevant information as long as the future is deterministic and well known. We use a network representation of uncertain quantities to model the uncertainty of the future. Information value is introduced as the likelihood of reaching a situation in the future where the information is relevant. The approach is demonstrated for the modelling of individual travel planning.Weniger anzeigen
Information systems’ (IS) design concerns modeling systems that are dynamic in nature. A dynamic system essentially has two dimensions of concern – static structure and dynamic behavior. The existence of dynamics – or interactions among parts of the system distinguish a dynamic system from a heap or collection of parts. Specification and management of the static aspects of an information system like the data and metadata have been fairly well addressed by existing paradigms. However, an understanding of the dynamic nature of information systems is still low. Currently most paradigms model behavioral properties above an existing structural model, resulting in what may be called “entity centric” modeling. Such a kind of modeling would neglect properties that can be attributed to behavioral processes themselves, and relationships that might exist among such processes. This thesis argues that the dynamics of an information system are best managed by explicitly characterizing an “interaction space” of the information system. An interaction space is defined as an abstract domain that represents the set of all dynamics of the information system. This is contrasted with an “entity space” that represents elements of the static structure of the information system. Recent results on the nature of interactive behavior and of open systems indicate that interaction spaces are characteristically different from the hierarchical nature of algorithmic problem solving. Interaction spaces consist of multiple interactive processes which affect the behavior of one another. Paradigms for the characterization of these spaces are hence explored as part of the thesis.Weniger anzeigen
The primary objective of this work is to develop a concept for a holistic data quality management which is based on formal data quality metrics and a well–defined process model. The extensive use of metadata provides a flexible adaptation to various application domains and a maximum degree of automation.
Turmoil in the business environment is driving manufacturing companies to become agile. Agility means the capability of operating profitably in a competitive environment of continuous and unpredictable changes with information systems regarded as one of its main enablers. The research presented in this work focuses on the assessment of information systems to support agile manufacturing. The assessment framework is constructed upon a series of competitive bases (six) and agility attributes (32) identified in the literature. Other issues included cover the characteristics of the business environment and the evolution/development and infrastructure of information systems. The framework is validated through a survey research instrument and the responses analysed with statistical tests (descriptive statistics, factor analysis, linear regression and reliability). The results of the statistical analysis enabled us to determine the attributes identified as predictors for the set of questions linking information systems and agile manufacturing. Due to the fuzzy nature of assessment of information systems, the complete framework can be presented as a hierarchy where techniques like AHP and fuzzy language sets are applicable. The findings will enable the researchers to clearly identify the trends adopted by manufacturing companies in the utilisation of information systems to gain competitive edge in support of the concept of agile manufacturing.Weniger anzeigen
Participative Enterprise Modelling (PEM) has been used in Information Systems Development and Business Development for some time now. Research has shown that the full and positive effects of PEM methods heavily depends on the ability of its users to manage situational factors, which characterise, influence and constrain development situations where it is used. Therefore, a shift must be made in method development, from the invention of new methods to the development of guidelines for the practical use of current methods in various situations. Such a shift calls for research into the complex relationships between situational factors in development processes. This paper discusses the challenges of investigating the impact of situational factors on PEM and outlines an approach to be used as part of ongoing research.Weniger anzeigen