Search

International audience; In recent years, data centers have witnessed an exponential growth for hosting hundreds of thousands of servers as well as to accommodating a very large demand for resources. To fulfill the required level of demand, some approaches tackled network aspects so to host a huge number of servers while others focused on delivering rapid services to the clients by minimizing the path length between any two servers. In general, network devices are often designed to achieve 1:1 oversubscription. Alternatively, in a realistic data center environment, the average utilization of a network could vary between 5% and 25%, and thus the energy consumed by idle devices is wasted. This paper proposes a new parameterizable data center topology, called PTNet. PTNet offers a gradual scalability that interconnects small to large networks covering different ranges of sizes. This new interconnection network provides also a small path length between any two servers even in large sized data centers. PTNet does not only reduce path length and latency, it also uses a power-aware routing algorithm which saves up to 40% of energy with an acceptable computation time. In comparison to existing solutions (e.g. Flatnet, BCube, DCell and Fat-tree), PTNet shows substantial improvements in terms of capacity, robustness, cost-effectiveness and power efficiency: this improvement reaches up to 50% in some cases. (C) 2017 Elsevier Inc. All rights reserved.

Contains fulltext : 35890.pdf (Publisher’s version ) (Closed access) On the Move to Meaningful Internet Systems 2006: OTM 2006 Workshops,Montpellier, France,, 29 oktober 2006

We present a new approach to anomaly-based network intrusion detection for web applications. This approach is based on dividing the input parameters of the monitored web application in two groups: the "regular" and the "irregular" ones, and applying a new method for anomaly detection on the "regular" ones based on the inference of a regular language. We support our proposal by realizing Sphinx, an anomaly-based intrusion detection system based on it. Thorough benchmarks show that Sphinx performs better than current state-of-the-art systems, both in terms of false positives/false negatives as well as needing a shorter training period.

The last years have seen the definition of many languages, models and standards tailored to specify and enforce access control policies, but such frameworks do not provide methodological support during the policy specification process. In particular, they do not provide facilities for the analysis of the social context where the system operates. In this paper we propose a model-driven approach for the specification and analysis of access control policies. We build this framework on top of SI*, a modeling language tailored to capture and analyze functional and security requirements of socio-technical systems. The framework also provides formal mechanisms to assist policy writers and system administrators in the verification of access control policies and of the actual user-permission assignment.

Two major problems in constructing data federations (for example, data warehouses and database federations) concern achieving and maintaining consistency and a uniform representation of the data on the global level of the federation. The first step in creating uniform representations of data is known as data extraction, whereas data reconciliation is concerned with resolving data inconsistencies. Our approach to constructing a global conceptual schema as the result of integrating a collection of (semantically) heterogeneous component schemas is based on the concept of exact views. We show that a global schema constructed in terms of exact views integrates component schemas in such a way that the global schema is populated by exactly those instances allowed by the local schemas (and in special cases, also the other way around). In this sense, the global schema is equivalent to the set of component schemas from which the global schema is derived. This paper describes a modeling framework for data federations based on the Object-Role Modeling (ORM) approach. In particular, we show that we can represent exact views within ORM, providing the means to resolve in a combined setting data extraction and reconciliation problems on the global level of the federation.

Business process models play an important role for the management, design, and improvement of process organizations and process-aware information systems. Despite the extensive application of process modeling in practice, there are hardly empirical results available on quality aspects of process models. This paper aims to advance the understanding of this matter by analyzing the connection between formal errors (such as deadlocks) and a set of metrics that capture various structural and behavioral aspects of a process model. In particular, we discuss the theoretical connection between errors and metrics, and provide a comprehensive validation based on an extensive sample of EPC process models from practice. Furthermore, we investigate the capability of the metrics to predict errors in a second independent sample of models. The high explanatory power of the metrics has considerable consequences for the design of future modeling guidelines and modeling tools.

This paper proposes an extension to the Object-Role Modeling approach to support formal declaration of dynamic rules Dynamic rules differ from static rules by pertaining to properties of state transitions, rather than to the states themselves In this paper, application of dynamic rules is restricted to so-called single-step transactions, with an old state (the input of the transaction) and a new state (the direct result of that transaction) Such restricted rules are easier to formulate (and enforce) than a constraint applying historically over all possible states In our approach, dynamic rules specify an elementary transaction type indicating which kind of object or fact is being added, deleted or updated, and (optionally) pre-conditions relevant to the transaction, followed by a condition stating the properties of the new state, including the relation between the new state and the old state These dynamic rules are formulated in a syntax designed to be easily validated by non-technical domain experts.

The emergence of Semantic Web (SW) and the related technologies promise to make the web a meaningful experience. Yet, high level modeling, design and querying techniques proves to be a challenging task for organizations that are hoping utilize the SW paradigm for their industrial applications, which are still using traditional database techniques. To address such an issue, in this paper, we propose a view model for the SW (SW-View), to SW-enable traditional solutions. First we outline the view model, its properties and some modeling issues, followed by some discussions on modeling such views (at the conceptual level). We also provide a brief discussion on how this view model is utilized in the design and construction of materialized ontology views to support extraction of sub-ontologies.

Information systems are facing conflicting requirements. On the one hand, systems need to be adaptive and self-managing to deal with rapidly changing circumstances. On the other hand, legislation such as the Sarbanes-Oxley Act, is putting increasing demands on monitoring activities and processes. As processes and systems become more flexible, both the need for, and the complexity of monitoring increases. Our earlier work on process mining has primarily focused on process discovery, i.e., automatically constructing models describing knowledge extracted from event logs. In this paper, we focus on a different problem complementing process discovery. Given an event log and some property, we want to verify whether the property holds. For this purpose we have developed a new language based on Linear Temporal Logic (LTL) and we combine this with a standard XML format to store event logs. Given an event log and an LTL property, our LTL Checker verifies whether the observed behavior matches the (un)expected/(un)desirable behavior.

It is well accepted that different types of distributed architectures require different levels of coupling. For example, in client-server and three-tier architectures the application components are generally tightly coupled between them and with the underlying communication middleware. Meanwhile, in off-line transaction processing, grid computing and mobile application architectures, the degree of coupling between application components and with the underlying middleware needs to be minimised along different dimensions. In the literature, terms such as synchronous, asynchronous, blocking, non-blocking, directed, and non-directed are generally used to refer to the degree of coupling required by a given architecture or provided by a given middleware. However, these terms are used with various connotations by different authors and middleware vendors. And while several informal definitions of these terms have been provided, there is a lack of an overarching framework with a formal grounding upon which software architects can rely to unambiguously communicate architectural requirements with respect to coupling. This paper addresses this gap by: (i) identifying and formally defining three dimensions of coupling; (ii) relating these dimensions to existing communication middleware; and (iii) proposing notational elements for representing coupling configurations. The identified dimensions provide the basis for a classification of middleware which can be used as a selection instrument.

Metadata management is a key issue in intelligent Web-based environments. It plays an important role in a wide spectrum of areas, ranging from semantic explication, information handling, knowledge management, multimedia processing to personalized service delivery. As a result, security issues around metadata management needs to be addressed in order to build trust and confidence to ambient environments. The aim of this paper is to bring together the worlds of security and XML-formatted metadata management in such a way that, on the one hand the requirement on secure metadata management is satisfied, while on the other other hand the efficiency on metadata processing can still be guaranteed. To this end, we develop an effective approach to enable efficient search on encrypted XML metadata. The basic idea is to augment encrypted XML metadata with encodings which characterize the topology and content of every tree-structured XML metadata, and then filter out candidate data for decryption and query execution by examining query conditions against these encodings. We describe a generic framework consisting of three phases, namely, query preparation, query pre-processing and query execution, to implement the proposed search strategy.

In this paper we argue that the effort within the context of Semantic Web research, such as RDF and DAML-S. will allow for better knowledge representation and engineering of educational systems and easier integration of e-learning with other business processes. We also argue that existing educational standards, such as SCORM and LOM could be mapped to those technologies, providing for more efficient automation of processes like educational resource annotation, and intelligent accessibility management. In this way we can use a successful combination of the technical advances outside of educational context and the existing educational standards, and allow for easier interoperability. To illustrate these issues and a solution approach we present the OntoAIMS educational environment.

During the development of theoretical frameworks researchers often graphically represent formal textual notations as part of a developed theory. This may lead to enrichments and new insights regarding a theory. A possibility for graphical representation of formalisms is the utilization of modeling languages such as ORM. This paper deals with the technique of visualizing formalisms by using ORM models and shows the advantages of graphically representing a formal theoretical framework. An application of the approach that has already been successfully practised is elaborated. This application concerns a theoretical framework consisting of knowledge intensive task properties and shows how the approach to visualize formalisms with ORM can be materialized.

Contains fulltext : 36033.pdf (Publisher’s version ) (Closed access)

Contains fulltext : 35834.pdf (Publisher’s version ) (Closed access) Contains fulltext : 35834.pdf (Author’s version postprint ) (Open Access)

This paper presents the realisation, using a Service Oriented Architecture, of an approach for dynamic flexibility and evolution in workflows through the support of flexible work practices, based not on proprietary frameworks, but on accepted ideas of how people actually work. A set of principles have been derived from a sound theoretical base and applied to the development of worklets, an extensible repertoire of self-contained sub-processes aligned to each task, from which a dynamic runtime selection is made depending on the context of the particular work instance. An erratum to this chapter can be found at http://dx.doi.org/10.1007/11914853_71.

Contains fulltext : 35489.pdf (Publisher’s version ) (Closed access)

Contains fulltext : 35813pre.pdf (Author’s version preprint ) (Open Access) Contains fulltext : 35813pub.pdf (Publisher’s version ) (Closed access)

Reference process models are templates for common processes run by many corporations. However, the individual needs among organizations on the execution of these processes usually vary. A process model can address these variations through control-flow choices. Thus, it can integrate the different process variants into one model. Through configuration parameters, a configurable reference models enables corporations to derive their individual process variant from such an integrated model. While this simplifies the adaptation process for the reference model user, the construction of a configurable model integrating several process variants is far more complex than the creation of a traditional reference model depicting a single best-practice variant. In this paper we therefore recommend the use of process mining techniques on log files of existing, well-running IT systems to help the reference model provider in creating such integrated process models. Afterwards, the same log files are used to derive suggestions for common configurations that can serve as starting points for individual configurations.

This paper provides formal semantics for an extension of the Object-Role Modeling approach that supports declaration of dynamic rules. Dynamic rules differ from static rules by pertaining to properties of state transitions, rather than to the states themselves. In this paper we restrict application of dynamic rules to so-called single-step transactions, with ail old state (the input of the transaction) and a new state (the direct result of that transaction). These dynamic rules further specify an elementary transaction type by indicating which kind of object or fact (being added, deleted or updated) is actually allowed. Dynamic rules may declare pre-conditions relevant to the transaction, and a condition stating the properties of the new state, including the relation between the new state and the old state. In this paper we provide such dynamic rules with a formal semantics based on sorted, first-order predicate logic. The key idea to our solution is the formalization of dynamic constraints as static constraints on the database transaction history.

A typical question for people dealing with administrative processes is: "When will my case be finished?". In this paper, we show how this question can be answered, using historic information in the form of event logs of the systems supporting these administrative processes. Many information systems record information about activities performed for past cases in logs. Hence, to provide insights into the remaining cycle time of a case, the current case can be compared to all past ones. The most trivial way of estimating the remaining cycle time of a case is by looking at the average cycle time and deducting the already past time of the case under consideration. However, in this paper we show how to compute the remaining cycle time using non-parametric regression on the data recorded in event logs. An experiment is presented that demonstrates that our techniques perform well on logs taken from practice.

Urge for comfort and excitement have made gadgets indispensable part of our life. The technology-enabled gadgets not only facilitate and enrich our daily lives but also are interesting tools to challenge human imagination to design and implement new ubiquitous applications. Pervasive gaming, in which human interaction and game/scenario-dependent designs are often common practices, has proved to be one of the areas to successfully combine technology and the human fantasy. By moving away from games being played by humans and by focusing instead on games played by robots and giving humans the leading role of defining game strategies and players’ roles, this paper aims at bridging the two fields of robotics and wireless sensor/actuator networks and exploring their potentials in the field of pervasive gaming. A generic game development framework is introduced that accommodates different types of robots and various kinds of sensors and actuators. Being extensible and modular, the proposed framework can be used for a wide range of pervasive applications built upon sensors and actuators. To enable game development, a Wiimote-based robot identification and localization technique is presented. The proposed framework and robot identification, localization, control and communication mechanisms are evaluated by implementing a game example.

While business processes are typically handled differently among companies, many of them are variations of a common process like procurement or invoicing. To gain synergy effects from corporate mergers, process analysts align such processes by identifying and seamlessly integrating overlapping process parts. To support this, we present in this paper an approach that merges two business process models which are depicted as Event-driven Process Chains into a single process model which can serve as a starting point for further process optimization. The approach has been implemented in the ProM process mining framework and can thus be used together with a wide range of other process mining and analysis techniques.