The visualization of spatio-temporal data helps researchers understand global processes such as animal migration. In particular, interactively restricting the data to different time windows reveals new insights into the short-term and long-term changes of the research data. Inspired by this use case, we consider the visualization of point data annotated with time stamps. We pick up classical, grid-based density maps as the underlying visualization technique and enhance them with an efficient data structure for arbitrarily specified time-window queries. The running time of the queries is logarithmic in the total number of points and linear in the number of actually colored cells. In experiments on real-world data we show that the data structure answers time-window queries within milliseconds, which supports the interactive exploration of large point sets. Further, the data structure can be used to visualize additional decision problems, e.g., it can answer whether the sum or maximum of additional weights given with the points exceed a certain threshold. We have defined the data structure general enough to also support multiple thresholds expressed by different colors.

The authors examine a particular type of domain-based metadata for which a complete ready-made conceptual framework is not and probably cannot be directly supported in predefined data models of knowledge-based representation paradigms. The data or knowledge base designer thus has the burden of sometimes working outside a familiar and otherwise appropriate model. The authors discuss issues arising in formulating certain domain-based metadata extensions and provide guidelines for developing them. These results derive from a continuing effort to create a knowledge base to support research on biological organisms. The added semantics are used to support a more flexible and reliable system for identification.>

A new method for computing minimal covers is presented using a new type of closure that allows significant reductions in the number of closures computed for normalizing relations. Benchmarks are reported comparing the new and the standard techniques.

A prototype database design system is presented. The system is object oriented in two ways. First, a uniform object-message paradigm is used for the design, definition, and manipulation language. Second, the structure of the underlying system is object oriented and is being implemented in Smalltalk-80.

We present a design system shell which can be used to experiment with principles of design and be used as a design tool where complex layers of information need to be specified about objects, such as in database design. The shell can be tailored to a variety of application areas. It is object-oriented in its implementation and structure. Objects and messages are used as the specification language. The basic ingredients of a rule-based production system are provided, with rules treated as objects and defined independently of the classes to which they are applied.