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.
9444422
A Systematic Approach to Flexible Specification, Composition, and Restructuring of Workflow Activities
We introduce the ActivityFlow specification language for flexible specification, composition, and coordination of workflow activities. The most interesting features of the ActivityFlow specification language include: (1) a collection of specification mechanisms, allowing workflow designers to use a uniform workflow specification interface to describe different types (i.e., ad-hoc, administrative, or production) of workflows involved in their organizational processesâ€“ this feature helps to increase the flexibility of workflow processes in accommodating various types of changes; (2) a set of activity modeling facilities, enabling workflow designers to describe the flow of work declaratively and incrementally, allowing to reason about correctness and security of complex workflow activities independently from their underlying implementation mechanisms; (3) an open architecture that supports user interaction as well as collaboration of workflow systems of different organizations, and a set of workflow activity restructuring operators to respond to dynamic changes of workflow activities. We end the paper with a series of simulation-based experiments that demonstrate the effectiveness of these restructuring operators and the implementation architecture of the ActivityFlow system.
11093943
Distributed query sampling: a quality-conscious approach
We present an adaptive distributed query-sampling framework that is quality-conscious for extracting high-quality text database samples. The framework divides the query-based sampling process into an initial seed sampling phase and a quality-aware iterative sampling phase. In the second phase the sampling process is dynamically scheduled based on estimated database size and quality parameters derived during the previous sampling process. The unique characteristic of our adaptive query-based sampling framework is its self-learning and self-configuring ability based on the overall quality of all text databases under consideration. We introduce three quality-conscious sampling schemes for estimating database quality, and our initial results show that the proposed framework supports higher-quality document sampling than existing approaches.
12098131
Context Cube: Flexible and Effective Manipulation of Sensed Context Data
In an effort to support the development of context-aware applications that use archived sensor data, we introduce the concept of the Context Cube based on techniques of data warehousing and data mining. Our implementation of the Context Cube provides a system that supports a multi-dimensional model of context data and with tools for accessing, interpreting and aggregating that data by using concept relationships defined within the real context of the application. We define the Context Cube information model, demonstrate functional applications that we have developed with the system, and explore possible applications that may be developed more easily using our tool.
2326738
Adaptable, efficient, and modular coordination of distributed extended transactions
The authors describe a method for building a variety of coordination protocols as well as distributed extended transaction primitives. The method is called open coordination protocol (OCP), and is applied to construct many variants of commit-transaction, as well as distributed split-transaction and distributed join-group. OCP adopts a modular decomposition of popular coordination protocols (e.g., two-phase commit) into microprotocols, and then chooses appropriate microprotocols to build new coordination protocols or extended transaction primitives with desired features (e.g., split-transaction with read-only optimization). They use incremental specialization to improve the efficiency of each implemented protocol.
26576594
OminiSearch: a method for searching dynamic content on the Web
To address the search problem over dynamic web pages, several domain-speci c information integration portal services have emerged, such as jango.excite.com and cnet.com. These integration services o er uniform access to heterogeneous collections of dynamic pages using wrapper technology. Common techniques used for constructing wrapper programs often require embedding programmers' understanding of the speci c presentation layout or speci c contents of the Web pages, often with the assistance of semi-automatic tools. However, even with partially automated tools, developing and maintaining wrappers turns out to be labor intensive and error-prone, especially for Web sites that are frequently changing their information presence on the Web. As a result, most information integration services are limited to a handful of sources and have a limited capability to e ectively incorporate additional or updated content providers into their existing integration access framework. The OminiSearch system demonstrates a method to incorporate new dynamic sources into an integration system in which useful data objects are extracted from dynamic Web pages without programmer intervention, and to maintain the capability to extract relevant information in the face of evolving structure in the Web sites.
8242993
Designing Web-Based Systems in Social Context: A Goal and Scenario Based Approach
In order to design a better web-based system, a designer would like to have notations to visualize how design experts’ know-how can be applied according to one’s specific social and technology situation. We propose the combined use of a goal-oriented language GRL and a scenarios-oriented notation UCM for representing design knowledge of web-based systems and information systems in general. Goals are used to depict business objectives, functional and non-functional system requirements. Tasks are used in the exploration of alternative technologies and their operationalizations into system constructs. Actors are used to do role-based analysis on social relationships. Scenarios are used to describe elaborated business processes or workflow. The approach is illustrated with an example of designing a web-based training system.
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
2115447
Security and privacy requirements analysis within a social setting
Security issues for software systems ultimately concern relationships among social actors stakeholders, system users, potential attackers - and the software acting on their behalf. We propose a methodological framework for dealing with security and privacy requirements based on i*, an agent-oriented requirements modeling language. The framework supports a set of analysis techniques. In particular, attacker analysis helps identify potential system abusers and their malicious intents. Dependency vulnerability analysis helps detect vulnerabilities in terms of organizational relationships among stakeholders. Countermeasure analysis supports the dynamic decision-making process of defensive system players in addressing vulnerabilities and threats. Finally, access control analysis bridges the gap between security requirement models and security implementation models. The framework is illustrated with an example involving security and privacy concerns in the design of agent-based health information systems. In addition, we discuss model evaluation techniques, including qualitative goal model analysis and property verification techniques based on model checking.
10661094
Designing information systems in social context: a goal and scenario modelling approach
In order to design a better information system, a designer would like to have notations to visualize how design experts' know-how can be applied according to one's specific social and technology situation. We propose the combined use of a goal-oriented requirements language (GRL) and a scenario-oriented notation Use Case Maps (UCM) for representing design knowledge of information systems. Goal-oriented modelling is used throughout the requirements and design process. In GRL, goals are used to depict business objectives and system requirements, both functional and non-functional. Tasks are used to represent different ways for achieving goals. Means-ends reasoning is used to explore alternative solutions and their operationalizations into implementable system constructs. Social context is modelled in terms of dependency relationships among agents and roles. Scenarios expressed in UCM are used to describe elaborated business processes or workflow. The complementary use of goal-oriented modelling with GRL and scenario modelling with UCM is illustrated with an example of designing a web-based training system.
42350068
Tackling the Infinite State Space of a Multimedia Control Protocol Service Specification
Coloured Petri Nets (CPNs) are used to model the service provided by an International Standard for the control of multimedia communications over telecommunication networks including the Internet, known as the Capability Exchange Signalling (CES) protocol. The state space of the CPN model includes all of the possible sequences of user observable events, known as the service language, which is a useful baseline against which the protocol can be verified. However, the CES service CPN possesses an infinite state space, due to unbounded communication channels. We parameterize the CPN with the channel capacity, propose and prove a recursive formula for its state space and provide an algorithm for its construction. The algorithm generates the state space for capacity l, from the state space for capacity l - 1, providing incremental state space generation rather than generating a new state space for each value of l. The state space is linear in the size of the channel.