8235954
Clustering spatial data using random walks
Discovering significant patterns that exist implicitly in huge spatial databases is an important computational task. A common approach to this problem is to use cluster analysis. We propose a novel approach to clustering, based on the deterministic analysis of random walks on a weighted graph generated from the data. Our approach can decompose the data into arbitrarily shaped clusters of different sizes and densities, overcoming noise and outliers that may blur the natural decomposition of the data. The method requires only O(n log n) time, and one of its variants needs only constant space.
2779311
The immune system as a reactive system: modeling T cell activation with statecharts
The construction of reliable reactive systems is considered to be one of the most challenging goals in the fields of software and system engineering. The definition of a reactive system suits biological systems at different levels, ranging from gene networks, developing embryos and the immune system. We report here the application of a tool developed for constructing computerized systems to the modeling and analysis of a biological system, the immune system. We use the language of statecharts within the framework of object-oriented modeling. The results described here indicate that this modeling strategy can contribute to the transition of biology from the phase of analysis to the phase of synthesis.
47242941
A Fast Multi-scale Method for Drawing Large Graphs
We present a multi-scale layout algorithm for the aesthetic drawing of undirected graphs with straight-line edges. The algorithm is extremely fast, and is capable of drawing graphs of substantially larger size than any other algorithm we are aware of. For example, the algorithm achieves optimal drawings of 1000 vertex graphs in about 2 seconds. The paper contains graphs with over 6000 nodes. The proposed algorithm embodies a new multi-scale scheme for drawing graphs, which was motivated by the recently published multi-scale algorithm of Hadany and Harel [7]. It can significantly improve the speed of essentially any force-directed method (regardless of that method's ability of drawing weighted graphs or the continuity of its cost-function).
1830823
Playing with time: on the specification and execution of time-enriched LSCs
We extend live sequence charts (LSCs), a highly expressive variant of sequence diagrams, with timing constructs, thus making the language suitable for specifying the behavioral requirements of time-intensive systems. We follow R. Alur and T.A. Henzinger (see Software Tools for Technology Transfer, vol.1, p.86-109, 1997) in basing the extension on a single clock object. We have implemented the extension in full in our play-engine tool, which provides user-friendly ways to play in the timing constraints, together with a powerful mechanism that can execute, or play out, the time-enriched requirements directly, without the need for an intra-object system model. It seems that in addition to many advantages in testing and requirements engineering, for some kinds of systems this could lead to the requirements actually serving as the final implementation.
8837470
Reactive Animation
Software engineers use system visualization mainly in two domains: algorithm visualization and system visualization, and both of these are often animated. In this paper we provide a generic link between the specification and animation of complex object-oriented reactive systems, which constitute one of the most important and difficult classes of systems. The link and its methodology form a basis for communication between standard reactive specification tools and standard animation tools. Reactive Animation can be used in a wide range of applications: computer games, navigation and traffic systems, interactive scientific visualization. Reactive Animation helps make the programming of such applications more reliable, expeditious and natural to observe and comprehend. We illustrate two examples: a complex biological model of thymic T-cell behavior and a traffic simulation. 3
10640301
Smart play-out
We describe "smart play-out", a new method for executing and analyzing scenario based behavior, which is part of the Play-In/Play-Out methodology and the Play-Engine tool. Behavior is "played in" directly from the system's GUI, and as this is being done the Play-Engine continuously constructs Live Sequence Charts (LSCs), a powerful extension of sequence diagrams. Later, behavior can be "played out" freely from the GUI, and the tool executes the LSCs directly, thus driving the system's behavior. An inherent difficulty in constructing a ``play-out" mechanism is how to resolve the nondeterminism allowed by the LSC specification in order to obtain an executable model. Smart play-out, is a recent strengthening of the play-out mechanism, which addresses this problem by using powerful verification methods, mainly model-checking, to execute and analyze the LSCs, helping the execution to avoid deadlocks and violations. Thus, smart play-out utilizes verification techniques to run programs, rather than to verify a program with respect to given requirements, as in traditional verification approaches. The ideas appear to be relevant in various stages of system development, including requirements specification and analysis, implementation and testing.
14408974
Towards an odor communication system
We propose a setup for an odor communication system. Its different parts are described, and ways to realize them are outlined. Our scheme enables an output device-the whiffer-to release an imitation of an odorant read in by an input device-the sniffer-upon command. The heart of the system is the novel algorithmic scheme that makes the scheme feasible. We are currently at work researching and developing some of the components that constitute the algorithm, and we hope that the description of the overall scheme in this paper will help to get other groups to join in this effort.