Web Services Communities: from Intra-Community Coopetition to Inter-Community Competition

This chapter discusses the structure and management of communities of Web services from two perspectives. The first perspective, called coopetition, shows the simultaneous cooperative and competitive behaviors that Web services exhibit when they reside in the same community. These Web services offer similar functionalities, and hence are competitive, but they can also cooperate as they share the same savoir-faire. The second perspective, called competition, shows the competition that occurs not between Web services but between their communities, which are associated with similar functionalities. To differentiate such communities, a competition model based on a set of metrics is discussed in this chapter

Quality Properties of Execution Tracing, an Empirical Study

The authors are grateful to all the professionals who participated in the focus groups; moreover, they also express special thanks to the management of the companies involved for making the organisation of the focus groups possible.Data are made available in the appendix including the results of the data coding process.The quality of execution tracing impacts the time to a great extent to locate errors in software components; moreover, execution tracing is the most suitable tool, in the majority of the cases, for doing postmortem analysis of failures in the field. Nevertheless, software product quality models do not adequately consider execution tracing quality at present neither do they define the quality properties of this important entity in an acceptable manner. Defining these quality properties would be the first step towards creating a quality model for execution tracing. The current research fills this gap by identifying and defining the variables, i.e., the quality properties, on the basis of which the quality of execution tracing can be judged. The present study analyses the experiences of software professionals in focus groups at multinational companies, and also scrutinises the literature to elicit the mentioned quality properties. Moreover, the present study also contributes to knowledge with the combination of methods while computing the saturation point for determining the number of the necessary focus groups. Furthermore, to pay special attention to validity, in addition to the the indicators of qualitative research: credibility, transferability, dependability, and confirmability, the authors also considered content, construct, internal and external validity

On The Assessment of Communities of Web Services

The notion of community of web services has been recently proposed and investigated to gather functionally similar web services in the same virtual space. This allows increasing the visibility of web services and their collaboration, which makes their discovery and composition easier. Using the community infrastructure, users are supposed to direct their requests to the community's manager (called master), that is in charge of selecting the appropriate web service. Because many communities providing the same functionality are available, selecting the best community to deal with, from the users and providers perspectives, is a key factor that still needs to be investigated. Another particularly challenging issue yet to be addressed is the selection by the master of the appropriate web service to be hosted in the community. Reputation has been proposed as a means to help users, providers, and masters evaluate and rank different candidates. However, reputation is mainly based on users feedback, which is not always accurate. Moreover, other performance parameters should be considered in the selection game. In this thesis, we propose a new assessment process that focuses on various performance aspects of the community rather than just its reputation. This assessment considers the performance parameters from the users, providers, and masters perspectives. In this approach, the communities performance rate is mainly based on the web services hosted by those communities. Such an assessment approach helps the master of the community differentiate between web services so that only the appropriate ones can be invited or accepted to join based on the communities requirements. It also helps the users and providers select the best available communities. The proposed method works on three steps. The first step focuses on defining and iv computing the evaluation metrics used in the assessment process while considering the requirements of all the stakeholders, namely users, providers, and communities. Thus, each community or web service is described by a vector of metrics. The second step includes the clustering of the evaluated communities and web services using the resulted vectors from the first step. During the third step, the resulting clusters are ranked using a function called goodness function. Web services and communities belonging to the best cluster are then selected. The effectiveness of the proposed assessment approach is tested by simulation and comparison to two other approaches in the literature

Scheduling Reputation Maintenance in Agent-based Communities Using Game Theory

In agent-based systems, agents can be organized within groups, called communities, where mem-bers are providing similar or complementary services. An example of such systems is agent-based communities of web services, where web services are abstracted as rational agents and empowered with decision making capabilities and can interact with each other. Managing reputation of each agent and of the whole community is a key issue towards securing this type of systems, where a con-troller agent is designed to observe and check the behavior of each member to update and maintain the system’s reputation. Scheduling the check (i.e. maintenance) by deciding about the moments where the check has to be done is still an open problem. Because it is highly expensive, maintenance cannot be done every moment or based on small history of agents’ behaviors. We propose in this thesis a scheduling algorithm that helps the controller agent improve the quality of the reputation mechanism, which increases the trust value of users toward the community. The proposed algorithm is based on a class of games called Bayesian Stackelberg. Our Bayesian Stackelberg game is designed between the controller agent and community members. We simulate and compare the efficiency of our algorithm with other stochastic techniques, namely uniform, normal and Poisson distributions. This research draws the lines for future work in the subject of optimizing reputation mechanisms through maintenance in different time intervals

Dynamic Formation and Strategic Management of Web Services Communities

In the last few years, communities of services have been studied in a certain numbers of proposals as virtual pockets of similar expertise. The motivation is to provide these services with high chance of discovery through better visibility, and to enhance their capabilities when it comes to provide requested functionalities. There are some proposed mechanisms and models on aggregating web services and making them cooperate within their communities. However, forming optimal and stable communities as coalitions to maximize individual and group efficiency and income for all the involved parties has not been addressed yet. Moreover, in the proposed frameworks of these communities, a common assumption is that residing services, which are supposed to be autonomous and intelligent, are competing over received requests. However, those services can also exhibit cooperative behaviors, for instance in terms of substituting each other. When competitive and cooperative behaviors and strategies are combined, autonomous services are said to be "coopetitive". Deciding to compete or cooperate inside communities is a problem yet to be investigated. In this thesis, we first identify the problem of defining efficient algorithms for coalition formation mechanisms. We study the community formation problem in two different settings: 1) communities with centralized manager having complete information using cooperative game-theoretic techniques; and 2) communities with distributed decision making mechanisms having incomplete information using training methods. We propose mechanisms for community membership requests and selections of web services in the scenarios where there is interaction between one community and many web services and scenarios where web services can join multiple established communities. Then in order to address the coopetitive relation within communities of web services, we propose a decision making mechanism for our web services to efficiently choose competition or cooperation strategies to maximize their payoffs. We prove that the proposed decision mechanism is efficient and can be implemented in time linear in the length of the time period considered for the analysis and the number of services in the community. Moreover, we conduct extensive simulations, analyze various scenarios, and confirm the obtained theoretical results using parameters from a real web services dataset

Game-Theoretic Foundations for Forming Trusted Coalitions of Multi-Cloud Services in the Presence of Active and Passive Attacks

The prominence of cloud computing as a common paradigm for offering Web-based services has led to an unprecedented proliferation in the number of services that are deployed in cloud data centers. In parallel, services' communities and cloud federations have gained an increasing interest in the recent past years due to their ability to facilitate the discovery, composition, and resource scaling issues in large-scale services' markets. The problem is that the existing community and federation formation solutions deal with services as traditional software systems and overlook the fact that these services are often being offered as part of the cloud computing technology, which poses additional challenges at the architectural, business, and security levels. The motivation of this thesis stems from four main observations/research gaps that we have drawn through our literature reviews and/or experiments, which are: (1) leading cloud services such as Google and Amazon do not have incentives to group themselves into communities/federations using the existing community/federation formation solutions; (2) it is quite difficult to find a central entity that can manage the community/federation formation process in a multi-cloud environment; (3) if we allow services to rationally select their communities/federations without considering their trust relationships, these services might have incentives to structure themselves into communities/federations consisting of a large number of malicious services; and (4) the existing intrusion detection solutions in the domain of cloud computing are still ineffective in capturing advanced multi-type distributed attacks initiated by communities/federations of attackers since they overlook the attacker's strategies in their design and ignore the cloud system's resource constraints. This thesis aims to address these gaps by (1) proposing a business-oriented community formation model that accounts for the business potential of the services in the formation process to motivate the participation of services of all business capabilities, (2) introducing an inter-cloud trust framework that allows services deployed in one or disparate cloud centers to build credible trust relationships toward each other, while overcoming the collusion attacks that occur to mislead trust results even in extreme cases wherein attackers form the majority, (3) designing a trust-based game theoretical model that enables services to distributively form trustworthy multi-cloud communities wherein the number of malicious services is minimal, (4) proposing an intra-cloud trust framework that allows the cloud system to build credible trust relationships toward the guest Virtual Machines (VMs) running cloud-based services using objective and subjective trust sources, (5) designing and solving a trust-based maxmin game theoretical model that allows the cloud system to optimally distribute the detection load among VMs within a limited budget of resources, while considering Distributed Denial of Service (DDoS) attacks as a practical scenario, and (6) putting forward a resource-aware comprehensive detection and prevention system that is able to capture and prevent advanced simultaneous multi-type attacks within a limited amount of resources. We conclude the thesis by uncovering some persisting research gaps that need further study and investigation in the future