1,720,993 research outputs found
Operational Semantics of Goal Models in Adaptive Agents
No full textSeveral agent-oriented software engineering methodologies address the emerging challenges posed by the increasing need of adaptive software. A common denominator of such methodologies is the paramount importance of the concept of goal model in order to understand the requirements of a software system. Goal models consist of goal graphs rep- resenting AND/OR-decomposition of abstract goals down to operationalisable leaf-level goals. Goal models are used primarily in the earlier phases of software engineering, for social modelling, requirements elicitation and analysis, to concretise abstract objectives, to detail them and to cap- ture alternatives for their satisfaction. Although various agent programming languages incorpo- rate the notion of (leaf-level) goal as a language construct, none of them natively support the definition of goal mod- els. However, the semantic gap between goal models used at design-time and the concept of goal used at implementa- tion and execution time represent a limitation especially in the development of self-adaptive and fault-tolerant systems. In such systems, design-time knowledge on goals and vari- ability becomes relevant at run-time, to take autonomous decisions for achieving high level objectives correctly. Recently, unifying operational semantics for (leaf) goals have been proposed (Riemsdijk, AAMAS08). We extend this work to define an operational semantics for the behaviour of goals in goal mod- els, maintaining the flexibility of using different goal types and conditions. We use a simple example to illustrate how the proposed approach effectively deals with the semantic gap between design-time goal models and run-time agent implementations
Goal-Oriented Development of Self-Adaptive Systems
No full textToday's software is expected to be able to work autonomously in an unpredictable environment, avoiding failure and achieving satisfactory performance. Self-adaptive systems try to cope with these challenging issues, autonomously adapting their behaviour to a dynamic environment to fulfil the objectives of their stakeholders. This implies that the software needs multiple ways to accomplish its purpose, enough knowledge of its construction, decision criteria for the selection of specific behaviours and the capability to make effective changes at runtime. The engineering of such systems is still challenging research in software engineering methods and techniques, as recently pointed out by the research community.
The objective of this thesis is twofold: First, to capture and detail at design time the specific knowledge and decision criteria needed for a system to guide adaptation at run-time.
Second, to create systems which are aware of their high-level requirements, by explicitly representing them as run-time objects, thus enabling it to act according to them and to monitor their satisfaction.
To deliver on this aim, we provide conceptual models and process guidelines to model at design time the knowledge necessary to enable self-adaptation in a dynamic environment, extending the agent-oriented software engineering methodology Tropos. The resulting framework, called Tropos4AS, offers a detailed specification of goal achievement, of the relationships with the environment, of possible failures and recovery activities.
A claim underlying the approach is that the concepts of agent, goal, and goal model, used to capture the system's requirements, should be preserved explicitly along the whole development process, from requirements analysis to the design and run-time, thus reducing the conceptual gaps between the software development phases, and providing a representation of the high-level requirements at run-time. A direct, tool-supported mapping from goal models to an implementation in a Belief-Desire-Intention agent architecture, and an operational semantics for goal model satisfaction at run-time, complement this work.
The framework is evaluated through application to research case studies and through an empirical study with subjects, assessing the usability and the comprehensibility of the modelling concepts
Personalizing Trust in Online Auctions
No full textThe amount of business taking place in online marketplaces such as eBay is growing rapidly. At the end of 2005 eBay Inc. reported annual growth rates of 42.5% [3] and in February 2006 received 3 million user feedback comments per day [1]. Now we are faced with the task of using the limited information provided on auction sites to transact with complete strangers with whom we will most likely only interact with once. People will naturally be comfortable with old fashioned "corner store" business practice [14], based on a person to person trust which is lacking in large-scale electronic marketplaces such as eBay and Amazon.com. We analyse reasons why the current feedback scores on eBay and most other online auctions are too positive. We introduce AuctionRules, a trust-mining algorithm which captures subtle indications of negativity from user comments in cases where users have rated a sale as positive but still voiced some grievance in their feedback. We explain how these new trust values can be propagated using a graph-representation of the eBay marketplace to provide personalized trust values for both parties in a potential transaction. Our experimental results show that AuctionRules beats seven benchmark algorithms by up to 21%, achieving up to 97.5% accuracy, with a false negative rate of 0% in comment classification tests compared with up to 8.5% from other algorithms tested
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Design Matters for Semantic Web Services
No full textThe several Semantic Web Services (SWS) initiatives seems to really pave the way for supporting autonomous and goal-oriented behavior during the whole service providing life-cycle. The main results based on service ontology languages, e.g., OWL-S, allow for automatic discover, invocation, and composition of services reducing the human intervention at a minimum.
Nevertheless, the SWS approaches have not focused enough on the analysis and design phases in order to support discover, composition, and the service ontology definition also at design time. On the contrary, our approach aims to illustrate possible advantages when considering the Tropos analysis and design levels over the SWS technologie
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Argumentation Semantics for Temporal Defeasible Logic
Full text linkWe present an extension of the argumentation semantics for defeasible logic to cover the temporalisation of defeasible logic with permanent and imminent temporal literals
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