Systems are more and more expected to work in dynamic environment, to deal with fluctuation of their characteristics and to guaranty functional and nonfunctional requirements. Systems should also keep compliant with the contracted quality of service. Moreover, when necessary, services and aspects should be added or removed on line. In this paper, we overview major approaches to deploy, reconfigure and adapt applications and underlying software platforms. These changes should be realized according to the evolving context and execution environment so that systems can stay compliant with the specifications and requirements of the application. We end this position paper with a vision on future directions and developments.

Electronic transactions with cryptocurrency systems based on blockchain in our days have become very popular due to the good reputation of this technology. However, that good reputation cannot deny the serious anomalies and the risks that can cause these cryptocurrencies. In this work, we propose a new model for anomaly detection over bitcoin electronic transactions. We used in our proposal two machine learning algorithms, namely the One Class Support Vector Machines (OCSVM) algorithm to detect outliers and the K-Means algorithm in order to group the similar outliers with the same type of anomalies. We evaluated our work by generating detection results and we obtained high performance results on accuracy.

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expressiveness according to the end-user preferences. We also define our QoS metrics and describe the tests in order to evaluate the implementation. At the end, we make a conclusion of of those preliminary tests. ABSTRACTThe spread of virtual environments is setting forth a new set of challenges in the management of system resources for guaranteeing Quality of Service (QoS). This paper describes an implementation of end-user 00s control to a Distributed Virtual Environment DVECOM MODELPlatform DVECOM [ChoukairOO]. In particular, we describe how to guarantee mandatory properties such as synchronization and consistency and how to reduce the impact on the application in case of sudden overload in the system and how we master this degradation to guarantee a smooth degradation according to the end user requirements. This representation degradation is driven by the user's choices and profile selected through the offered rendering strategy API. We also present our evaluation of the QoS implementation, describing some interesting results we achieved in a simulation of a collaborative work in the system. 111 0-7695-0568-6/00 $10.00 0 2000 IEEE

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