12929111
Type Safety in the Context of Method Updates
This paper presents a framework for checking and maintaining type safety in the presence of method evolution. A method update often affects all components of the method, including the inter face and the implementation. The type safety problem is addressed as two levels of type consistency. The first level relates to the type checking of methods in the context of the class inheritance hierarchy, and concerns the semantics of the polymorphism of methods. The second level considers the implementation parts of methods by capturing and preserving the semantics of the chain of calling relationships among relevant methods. A graph-based approach is used to achieve this two-level type consistency required at the level of class inheritance hierarchy and the level of method invocation. We demonstrate that the two levels of type consistency checking combined provide a better control of the run-time type error problems.
9143242
Update Monitoring: The CQ Project
In rapidly growing open environments such as the Internet, users experience information starvation in the midst of data overload, due to difficulties similar to finding the needle in a haystack. Update monitoring is a promising area of research where we bring the right information to the user at the right time, instead of forcing the user through manual browsing or repeated submission of queries. As an example of update monitoring research, we outline our work in the Continual Queries (CQ) project, including its basic concepts, software architecture, and current implementation status.
599285
Differential evaluation of continual queries
We define continual queries as a useful tool for monitoring of updated information. Continual queries are standing queries that monitor the source data and notify the users whenever new data matches the query. In addition to periodic refresh, continual queries include Epsilon Transaction concepts to allow users to specify query refresh based on the magnitude of updates. To support efficient processing of continual queries, we propose a differential re-evaluation algorithm (DRA), which exploits the structure and information contained in both the query expressions and the database update operations. The DRA design can be seen as a synthesis of previous research on differential files, incremental view maintenance, and active databases.
3582970
Building a Semantic Web System for Scientific Applications: An Engineering Approach
This paper presents an engineering experience for building a Semantic Web compliant system for a scientific application – agricultural zoning. First, we define the concept of ontological cover and a set of relationships between such covers. These definitions, based on domain ontologies, can be used, for example, to support the discovery of services on the Web. Second, we propose a semantic acyclic restriction on ontologies which enables the efficient comparison of ontological covers. Third, we present different engineering solutions to build ontology views satisfying the acyclic restriction in a prototype. Our experimental results unveil some limitations of the current Semantic Web technology to handle large data volumes, and show that the combination of such technology with traditional data management techniques is an effective way to achieve highly functional and scalable solutions.
13182282
InfoFilter: Supporting quality of service for fresh information delivery
With the explosive growth of the Internet and World Wide Web comes a dramatic increase in the number of users that compete for the shared resources of distributed system environments. Most implementations of application servers and distributed search software do not distinguish among requests to different web pages. This has the implication that the behavior of application servers is quite unpredictable. Applications that require timely delivery of fresh information consequently suffer the most in such competitive environments. This paper presents a model of quality of service (QoS) and the design of a QoS-enabled information delivery system that implements such a QoS model. The goal of this development is two-fold. On one hand, we want to enable users or applications to specify the desired quality of service requirements for their requests so that application-aware QoS adaptation is supported throughout the Web query and search processing. On the other hand, we want to enable an application server to customize how it should respond to external requests by setting priorities among query requests and allocating server resources using adaptive QoS control mechanisms. We introduce the Infopipe approach as the systems support architecture and underlying technology for building a QoS-enabled distributed system for fresh information delivery.
12589406
VISTA: Validating and Refining Clusters Via Visualization
Clustering is an important technique for understanding of large multidimensional datasets. Most of clustering research to date has been focused on developing automatic clustering algorithms and cluster validation methods. The automatic algorithms are known to work well in dealing with clusters of regular shapes, for example, compact spherical shapes, but may incur higher error rates when dealing with arbitrarily shaped clusters. Although some efforts have been devoted to addressing the problem of skewed datasets, the problem of handling clusters with irregular shapes is still in its infancy, especially in terms of dimensionality of the datasets and the precision of the clustering results considered. Not surprisingly, the statistical indices works ineffective in validating clusters of irregular shapes, too. In this paper, we address the problem of clustering and validating arbitrarily shaped clusters with a visual framework (VISTA). The main idea of the VISTA approach is to capitalize on the power of visualization and interactive feedbacks to encourage domain experts to participate in the clustering revision and clustering validation process. The VISTA system has two unique features. First, it implements a linear and reliable visualization model to interactively visualize multi-dimensional datasets in a 2D star-coordinate space. Second, it provides a rich set of user-friendly interactive rendering operations, allowing users to validate and refine the cluster structure based on their visual experience as well as their domain knowledge.
18066023
Improvement on vertex cover for low-degree graphs
The Vertex Cover problem (given a graph G and an integer k, decide if G has a vertex cover of k vertices) is one of the six “basic” NP-complete problems according to Garey and Johnson [7]. It is fixed-parameter tractable in terms of Downey and Fellows [5], that is, it can be solved in time O(f(k)n), where f is a function of the parameter k but independent of the input length n and c is a constant independent of the parameter k. Continuous efforts have been made in improving fixed-parameter tractable algorithms for the vertex cover problem, starting from Buss’ algorithm of running time O(kn + 2kk2k+2) [2]. Downey and Fellows [4] developed an O(kn + 2kk2) time algorithm. More recently, Balasubramanian et al. [1] developed an O(kn+1.3247kk2) time algorithm. Later Downey et al. [6] improved the result slightly to time complexity O(kn + 1.3195kk2), and Niedermeier and Rossmanith [9] developed an algorithm of time O(kn+1.2918kk2). More recently, Chen et al. [3] developed an O(kn + 1.271kk2) time algorithm. For the restricted version of the vertex
7311513
Polygonal Shape Blending with Topological Evolutions
This paper presents a new general approach to blend 2D shapes with different topologies. All possible topological evolutions are classified into three types by attaching three different topological cells. This formalism is resulted from Morse theory on the behavior of the 3D surface around a non-degenerate critical point. Also we incorporate degenerate topological evolutions into our framework which produce more attractive morphing effects. The user controls the morph by specifying the types of topological evolutions as well as the feature correspondences between the source and target shapes. Some techniques are also provided to control the vertex path during the morphing process. The amount of user input required to produce a morph is directly proportional to the amount of control the user wishes to impose on the process. The user may allow the system to automatically generate the morph as well. Our approaches are totally geometric based and are easy and fast enough in fully interactive time. Many experimental results show the applicability and flexibility of our approaches.
45704904
Automatic Deformable Shape Segmentation for Image Database Search Applications
A method for shape based image database indexing is described. Deformable shape templates are used to group color image regions into globally consistent configurations. A statistical shape model is used to enforce the prior probabilities on global, parametric deformations for each object class. The segmentation is determined in part by the minimum description length (MDL) principle. Once trained, the system autonomously segments deformed shapes from the background, while not merging them with adjacent objects or shadows. The formulation can be used to group image regions based on any image homogeneity predicate; e.g., texture, color, or motion. Preliminary experiments in color segmentation and shape-based retrieval are reported.
17865149
A framework for specification-based class testing
Class testing is the base of object-oriented software testing. It involves three aspects: testing each method, testing the relations among class methods and testing the inheriting relation between class and subclass. Rather than concerning the whole class testing process, most specification-based class testing focuses on the methods of generating test cases from the class specification. As a result, the class testing process and test cases cannot be unified and managed in a consistent and convenient way. This paper introduces a test class framework (TCF) that is used to structure the test cases and test deriving process of the class under testing. This framework clearly denotes the process of deriving test cases and test suites from a class specification. It facilitates the construction and management of test cases. Object-Z notation is used to express the framework and class specification.
35610063
A Specification-Based Approach to Testing Polymorphic Attributes
The object-oriented features, such as aggregation, inheritance and polymorphism, facilitate software reuse and improve software quality. But those features also cause new problems that traditional testing techniques cannot resolve effectively. Existing researches on object-oriented software testing are mainly based on some graph representations and seldom consider the combinational effect of aggregation, inheritance and polymorphism. For some model-based specifications that do not include graph representations, it is difficult to use the graph based testing techniques to derive test cases. This paper provides an approach to deriving test cases for testing the combinational effect of aggregation, inheritance and polymorphism from a model-based class specification. This approach contains two techniques at intra-class and inter-class testing levels and is mechanized using the algorithms presented in this paper. Finally, through the experimental analysis, we present the effectiveness and applicability of our testing approach.