A key feature for most collaborative applications is their ability to distinguish access rights to shared documents in a dynamic group of collaborators. To achieve high availability and avoid single points of failure, systems can replicate this access control policy across sites. Increasingly, Conflict-free Replicated Data Types (CRDTs) are used to this end. They embed conflict resolution strategies that take into account concurrent modifications to the policy but also to the document that it manages. However, few systems in the literature support multiple administrators, and those which do fall short of considering distributed applications where no node or group of nodes is central to its operation. To allow multiple concurrent edits of the policy in massively collaborative settings with no central server, we devise a specialized causal model that minimizes concurrency. Crucially our model allows to correct the document state in case operations have become unauthorized following a policy change. We apply our model to a CRDT replicating an access control policy with read and write rights on a collaborative document and admin rights on the policy. We end by studying flexible conflict resolution strategies, providing our underlying algorithms.

To achieve high availability, large-scale distributed systems have to replicate data and to minimise coordination between nodes. For these purposes, literature and industry increasingly adopt Conflict-free Replicated Data Types (CRDTs) to design such systems. Conflict-free Replicated Data Types (CRDTs) are new specifications of existing data types, e.g., Set or Sequence. While CRDTs have the same behaviour as previous specifications in sequential executions, they actually shine in distributed settings as they natively support concurrent updates. To this end, CRDTs embed in their specification conflict resolution mechanisms. These mechanisms usually rely on identifiers attached to elements of the data structure to resolve conflicts in a deterministic and coordination-free manner. Identifiers have to comply with several constraints, such as being unique or belonging to a dense total order. These constraints may hinder the identifier size from being bounded. Identifiers hence tend to grow as the system progresses, which increases the overhead of CRDTs over time and leads to performance issues. To address this issue, we propose a novel Sequence CRDT which embeds a renaming mechanism. It enables nodes to reassign shorter identifiers to elements in an uncoordinated manner. Experimental results demonstrate that this mechanism decreases the overhead of the replicated data structure and eventually minimises it.

Information leakages are one of the main security threats in today's Internet. As ICN is expected to become the core architecture for Future Internet, it is therefore mandatory to prevent this threat. This paper proves that some ICN configuration prevents information leakages via Data packets and shows that it is an open problem to prevent interest packets from carrying encoded crucial information in their names. Assuming that names in ICN will follow the current URL format commonly used in the Internet, we get the statistics of web URL based on extensive crawling experiments of main internet organizations. Then we propose a simple filtering technique based on these statistics for firewall to detect anomalous names in ICN. The experiment shows that our filtering technique recognizes 15% of names in our dataset as malicious. As the false positive rate is still high for this filter to be used in a real world operation, this work is an important step for detecting anomalous names and preventing information-leakage in ICN.

Collaborative environments have put an enormous challenge to secure the information processing systems being used to manage them. Challenges to provide secure framework are amplified when it comes to the domain of flexible and distributed systems as the trust, temporal and performance related aspect

Cross-organizational service-based processes are increasingly adopted by different companies when they can not achieve goals on their own. In order to guarantee that all involved partners are informed about errors that may happen in the collaboration, it is necessary to monitor the execution process by continuously observing and checking message exchanges during runtime. This allows a global process tracking and evaluation of process metrics. In this paper, we present an approach for decentralized monitoring of cross-organizational choreographies. We introduce the concept of External Flow Monitoring and define a hierarchical propagation model for exchanging external notifications between the collaborating parties. We also introduce the concept of EFM-view which allows partners to track the state of the choreography beyond their own processes. The collected monitoring data can be further used for the evaluation of global process metrics by expressing and evaluating statistical queries over execution traces.

In this paper, we propose an approach for the verification of declarative Web services composition processes using satisfiability solving. The need for the satisfiability solving approach stems from the nature of declarative processes which are defined by only specifying the constraints that mark the boundary of the solution to the composition process. As a result the state space of a declarative process can be significantly large, as the process is only partially defined and all the transitions have not been explicitly defined. Further, as the conflict clauses returned by the SAT solver can be significantly large for complex processes and verification requirements, we propose a filtering criteria and defined patterns for identifying the clauses of interest for process verification.

Every company wants to improve the way it does business, or produce things more efficiently, and make greater profit. Therefore, business processes have become subject to evolutionary changes, which in turn increase the need for an efficient change support. In this sense, many researches were conduc

In this paper, we propose an event-based framework that allows to specify and reason about the monitoring properties during composition process execution. The proposed approach is highly expressive and allows to specify monitoring properties that can be based on either functional or non-functional requirements, allows multi-level detection of any violation, allows to calculate effects of any such violation on the overall process execution and to recover from it using a set of recovery actions. The choice of a reasoning based approach allows to foresee the effects of violations and respects any functional and non-functional constraints associated with the process, when performing recovery. In addition, as the approach builds upon an event-based declarative framework called DISC, it results in an integrated approach as both composition design and monitoring framework are event-based.

Web services are defined independently of any execution context. Due to their inherent autonomy and heterogeneity, it is difficult to examine the behaviour of composite services, especially in case of failures. This paper is interested in ensuring composite services reliability. Reliable composition is defined as a composition where all instance executions are correct from a transactional and business point of view. In this paper, the authors propose a transactional approach for ensuring reliable Web service compositions. The approach integrates the expressivity power of workflow models and the reliability of Advanced Transactional Models (ATM). This method offers flexibility for designers to specify their requirements in terms of control structure, using workflow patterns, and execution correctness. Contrary to ATM, the authors start from the designers’ specifications to define the appropriate transactional mechanisms that ensure correct executions according to their requirements.

Web services composition design, verification and monitoring are active and widely studied research directions. Little work however has been done in integrating these related dimensions using a unified formalism. In this paper we propose a declarative event-oriented framework, called DISC, that serves as a unified framework to bridge the gap between the process design, verification and monitoring. Proposed framework allows for a composition design to accommodate various aspects such as data relationships and constraints, Web services dynamic binding, compliance regulations, security or temporal requirements and others. Then, it allows for instantiating, verifying and executing the composition design and for monitoring the process while in execution. The effect of run-time violations can also be calculated and a set of recovery actions can be taken, allowing for the self-healing Web services composition.

SOA have been deployed as a mean to offer a better flexibility, to increase efficiency through reuse of services and also to improve interoperability by providing new opportunities to connect heterogeneous platforms. However, those benefits make security more difficult to control. Fortunately, new standards are proposed to treat this issue, but their current use makes the architecture much more complex and challenges the characteristics of SOA. In this paper, we address this issue by separating security services from business ones and organizing the architecture referring to the principle of separation of concerns. Next, we propose a new model which consists of three components: business services, security meta-services and an orchestration service. Then, we show that the architecture remains secure while enforcing its flexibility and agility.

Web services are becoming one of the main technologiesfor designing and building complex inter-enterprise businessapplications. Usually, a business application cannot be fulfilled by one Web service but by a combination of severalones. Hence, there is an obvious need for mechanisms allowing Web services composition. In this paper, we are interested in the automatic composition of Web services. Ourcomposition framework is based on the coordination of Webservices having the capability to communicate via the exchange of messages. Web services are modeled as conversational automata, where transitions are possibly guarded according to the values of exchanged or produced data. If the coordination does not satisfy the business application, we synthesize a new service called mediator. The mediator aims at generating the missing messages which are required to complete the cartesian product so that it mimics the goal service representing the business application to implement.

Reliability is one of the main challenge that encounter Web servicescompositions. Due to the inherent autonomy and heterogeneity of Webservices it is difficult to predict the behavior of the overallcomposite service.Current related technologies are unable to resolve this problemefficiently. These technologies rely on two existing strongapproa-ches: transactional processing and workflow systems. In onehand transactional processing ensures reliability. However, they aretoo rigid to support process based applications like composite Webservices. On the other hand, workflow systems focus mainly oncoordination and organizational aspects and ignore reliabilityissues.In this paper we propose a new solution that combines the businessprocess adequacy of workflow systems and the reliability oftransactional processing. We introduce the concept of transactionalpatterns to ensure reliable composite services. A transactionalpattern can be seen as a convergence concept between workflowpatterns and advanced transactional models. We show how we use it todefine composite services and how we ensure their reliabilityaccording to the designers specific needs.

The recent evolution of Internet, driven by the Web services technology, is extending the role of the Web from a support of information interaction to a middleware for B2B interactions.Indeed, the Web services technology allows enterprises to outsource parts of their business processes using Web services. And it also provides the opportunity to dynamically offer new value-added services through the composition of pre-existing Web services.In spite of the growing interest in Web services, current technologies are found lacking efficient transactional support for composite Web services (CSs).In this paper, we propose a transactional approach to ensure the failure atomicity, of a CS, required by partners. We use the Accepted Termination States (ATS) property as a mean to express the required failure atomicity.Partners specify their CS, mainly its control flow, and the required ATS. Then, we use a set of transactional rules to assist designers to compose a valid CS with regards to the specified ATS.

Current workflow models are mainly concerned with the automation of administrative and production business processes. These processes coordinate well-defined activities which execute in isolation, i.e. synchronize only at their start/terminate states. If these models can be applied efficiently for a class of applications, they show their limits when one wants to model the subtlety of cooperative interactions as they occur in more creative processes, typically co-design and co-engineering processes. In this paper, we introduce the concept of cooperative workflow, i.e. a workflow model which extends classical workflow models with capabilities to synchronize activities interacting not only when they start and when they terminate, but also at any point of their execution. In the spirit of the workflow approach, the modelling and enactment of cooperative workflows must remain simple.