1514813
Temporal Query Processing Using Spatially-Partitioned Method
In this paper, we propose a general spatiallypartitioned temporal operation model, called 3D-TOM, and partition-based join algorithms for various types of temporal join in the proposed model. The temporal operators addressed in this paper include overlap, precede, follow, and equal. Some factors which a ect the performance of the proposed method are also discussed.
1231793
An effective data clustering measure for temporal selection and projection queries
Abstract Temporal databases (TDBs) allow users to record and retrieve time-varying data objects. Since TDBs usually manage a huge amount of underlying data objects, efficient disk accesses are essential for fast response time in temporal query processing. Data clustering is one of the most effective techniques that can improve performance of TDB systems. However, clustering measures for conventional data objects are not appropriate to temporal data objects because it is important to exploit temporal properties of underlying data objects and temporal queries as data clustering criteria. In this paper, we propose a data clustering measure called temporal affinity that can be used for effective temporal data clustering. The temporal affinity, which is based on the semantics of temporal operators, reflects the closeness among temporal data objects with respect to temporal query processing. We perform experiments to show the effectiveness of the proposed temporal data clustering measure. The experimental results indicate that a data clustering method based on the temporal affinity works better than other methods.
1994375
Effective Temporal Aggregation Using Point-Based Trees
Temporal databases introduce the concept of time into underlying data, and provide built-in facilities that allow users to store and retrieve time-varying data. The aggregation in temporal databases, that is, temporal aggregation is an extension of conventional aggregation on the domain and range of aggregates to include time concept. Temporal aggregation is important for various applications, but is very expensive. In this paper, we propose a new tree structure for temporal aggregation, called PA-tree, and aggregate processing method based on the PA-tree. We show that the time complexity of the proposed method is better than those of the existing methods. The time complexity of the proposed method is shown to be indeed the lower bound of the problem. We perform comparative experiments and show the performance advantage of our proposed method in practice.
26955217
On Temporal Aggregate Processing Based on Time Points
Temporal aggregation is an extension of conventional aggregate on the domain and range of aggregates to include the time concept. In this paper, we propose a new tree-based temporal aggregation processing method. The time complexity of the proposed method is better than those of the existing methods. The experimental results indicate that our proposed method ourperforms the existing methods.
12043862
A method and tool support for variant requirements analysis: goal and scenario based approach
Identifying and representing variant requirements among products in a product family are crucial activities for a successful software reuse. The variant requirements should be not only identified based on the business goal, which drives marketing plan, product plan, and differences among products, but also represented as familiar notations in order to support developing a particular product in the product family. Thus, our proposal is to identify the variant requirements through goals and scenarios, and represent them as variable use cases for a product family. Especially, for identification of the variant requirements, we propose four abstraction levels of requirements in the product family, and goal and scenario modeling. For representation of them, variable use case model is suggested, and also the use case transfer rules are proposed so as to bridge the gap between the identification and representation activity. The paper illustrates the application of the approach within a supporting tool, namely DREAM (Domain REquirements Analysis Method) using the ATM example.
241209
Transient behaviors of TCP-friendly congestion control protocols
We investigate the fairness, smoothness, responsiveness, and aggressiveness of TCP and three representative TCP-friendly congestion control protocols: GAIMD, TFRC, and TEAR. The properties are evaluated both analytically and via simulation by studying protocol responses to three network environment changes. The first environment change is the inherent fluctuations in a stationary network environment. Under this scenario, we consider three types of sending rate variations: smoothness, short-term fairness, and long-term fairness. For a stationary environment, we observe that smoothness and fairness are positively correlated. We derive an analytical expression for the sending rate coefficient of variation for each of the four protocols. These analytical results match well with experimental results. The other two environment changes we study are a step increase of network congestion and a step increase of available bandwidth. Protocol responses to these changes reflect their responsiveness and aggressiveness, respectively.
8963340
Understanding and Aiding Code Evolution by Inferring Change Patterns
Evolution continues to play an ever-increasing role in software engineering. Although changing a program is the core of software evolution, program change patterns have not been considered as a first class entity in most classic studies of software evolution. Past empirical studies of software evolution primarily relied on quantitative and statistical analyses of a program over time, but did not focus on semantic and qualitative change patterns of a program. We hypothesize that by treating change patterns as first class entities we can better understand software evolution and also aid programmers in changing software. Our goal is to infer clone evolution patterns from a set of program versions stored in a source code repository. We defined a set of common clone evolution patterns based on our insights from the copy and paste study.
7719896
A study of evolution in the presence of source-derived partial design representations
When performing evolution tasks, software engineers focus on both the low-level changes required and the effects those changes will have on the system's design. The Design Snippets Tool generates partial design representations intended to help engineers address one design criterion: ease of change. We describe a study in which participants used the Design Snippets Tool and other aids to perform a restructuring task focused on ease of change. Our findings describe how participants proceeded through the restructuring task and how they used the Design Snippets Tool. The results show that participants used the Design Snippets Tool for high-level tasks such as discovery of design problems, identification of restructuring goals, and confirmation of design improvements.
46306635
A Blind Watermarking for 3-D Dynamic Mesh Model Using Distribution of Temporal Wavelet Coefficients
In this paper, we present a watermarking method for 3-D mesh sequences with a fixed connectivity. The main idea is to transform each coordinate of vertex with the identical connectivity index along temporal axis using wavelet transform and modify the distribution of wavelet coefficients in temporally high (or middle)-frequency frames according to watermark bit to be embedded. Due to the use of the distribution, our method can retrieve the hidden watermark without any information about original mesh sequences in the process of watermark detection. To increase the watermark capacity, all vertices are divided into groups, namely bins, using the distribution of scaling coefficients in low-frequency frames. As the vertices with the identical connectivity index over whole frames belong to one bin, their wavelet coefficients are also assigned into the same bin. Then, the watermark is embedded into each axis of the wavelet coefficients. Through simulations we show that the proposed is fairly robust against various attacks that are probably concerned in copyright protection of 3-D mesh sequences.