Tilmann Zäschke

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We propose the PATRICIA-hypercube-tree, or PH-tree, a multi-dimensional data storage and indexing structure. It is based on binary PATRICIA-tries combined with hypercubes for efficient data access. Space efficiency is achieved by combining prefix sharing with a space optimised implementation. This leads to storage space requirements that are comparable or(More)
Many object-oriented software systems rely on persistent data. Such systems also evolve over time. These two equally valid needs clash: a system may attempt to retrieve data whose description in the program has changed. A typical scenario involves an object retrieval failure because of an evolution in the corresponding class. Another, more critical one(More)
We propose an approach to optimising schema evolution operation sequences in object databases. The approach separates operations that add structures from those that remove structures so that all additions are performed before any removals. This separation ensures that there is always a state during schema evolution where data can be evolved from structures(More)
The storage and management of multi-dimensional data is an important aspect in many applications, like geo-information systems, computer vision and computer geometry. In contemporary times, when computers are able to capture and store increasing amounts of multidimensional data, it is important for applications to efficiently store and query this data. This(More)
Based on a real-world case study in agile development, we examine issues of schema evolution in state-of-the-art object databases. In particular, we show how traditional problems and solutions discussed in the research literature do not match the requirements of modern agile development practices. To highlight these discrepancies, we present the approach to(More)