Mitteilungen des URZ 2/2002 (Inhalt siehe Schlagwörter)

Intranet - Erwartungen und Entwicklungen JavaOS - ein Betriebssystem fuer Intranets Network Computer - Eine Verkaufsstrategie? Was gibt es schon? Netscape IFC's - Gestalten von graphische Nutzerinterfaces WWW-Sicherheitsaspekte - ein heisses Thema: Sicherheit im Netz Aufbau einer Certification Authority - z.B. IN e.V. Chemnitz Authentisierung und Verteilung von Konfigurationsfiles - am Bsp. URZ

Mitteilungen des URZ 2/2002 (Inhalt siehe Schlagwörter)

Dynamic address assignment is one of the most important features in wireless ad hoc networks if nodes should be enabled to join and to work in the network by automatically configuring all necessary settings. Different approaches have been developed throughout the last years to achieve this objective of Dynamic Address Autoconfiguration but research primarily focused on efficiency and correctness, less on security issues. Whereas Duplicate Address Detection has become reliable in commonplace scenarios, it is still relatively easy to suspend the whole network functionality in extraordinary situations within the boundaries of a Dynamic Address Configuration Protocol. In this paper, we therefore want to point out shortcomings and weaknesses in existing protocol solutions which address dynamic IP address assignment. We concentrate on a leader-based approach called ODACP and want to propose several solutions which improve the original protocol in such a way that it is safer against malicious host activities. Finally, we will demonstrate the improvements of our solution in a separate test scenario.

Die vorliegende Broschüre beinhaltet zu fünf ausgewählten Beispielen der Sanierung aktuelle Biomonitoring-Ergebnisse und stellt erste Betrachtungen zu Biodiversität und Nachhaltigkeit der Entwicklung von Ökosystemen in den Bergbaufolgelandschaften des ehemaligen Uranerzbergbaues in Sachsen und Thüringen dar.

Alternative Geschäftsmodelle wie Software as a Service (SaaS) und Open-Source-Software (OSS) steigern die Attraktivität von Enterprise Resource Planning (ERP) Systemen für Kleine und Mittelständische Unternehmen (KMU). Jedoch stellen die Beratungsleistungen, die für die Konfiguration eines ERP-Systems zur Anpassung an die spezifischen Bedürfnisse eines Unternehmens notwendig sind, eine hohe Einführungshürde dar. Eine Konfigurationsoption, die bei vielen ERP-Systemen eine Rolle spielt, ist die Kategorienkonfiguration. Mit Hilfe einer automatisierten Konfigurationsunterstützung können Geschäftsführer von kleinen Unternehmen die Kategorienkonfiguration selbst durchführen und einen Teil der Einführungskosten einsparen. Im Rahmen der kumulativen Dissertation werden Automatisierungsansätze zur Konfigurationsunterstützung für die ERP-Kategorienkonfiguration generiert und auf das Open-Source ERP-System ERP5 angewandt. Die Automatisierungsansätze basieren auf Ähnlichkeitsberechnungen zu Falldatensätzen von 235 Unternehmen, Kategorien-Konsolidierung durch Umleitungsinformationen in Wikipedia-Artikeln, Templates und Meta-Templates. Die empirische Evaluation in einem Laborexperiment mit 100 Teilnehmern und eine Umfrage bestätigen die Gültigkeit, Nützlichkeit und Effektivität der generierten Ansätze. Die Konfigurationsunterstützung kann durch einen standardisierten Beratungsprozess und die Vermittlung des für eine konkrete ERP-Einführung notwendigen Wissens mittels Massenindividualisierung ergänzt werden. Dieser Ansatz wurde mit und für ERP5 umgesetzt und lässt sich auch auf andere Open-Source-Projekte übertragen.

Mobility-Based Routing Overhead Management in Reconfigurable Wireless Ad Hoc Networks Routing Overheads are the non-data message packets whose roles are establishment and maintenance of routes for data packets as well as neighbourhood discovery and maintenance. They have to be broadcasted in the network either through flooding or other techniques that can ensure that a path exists before data packets can be sent to various destinations. They can be sent reactively or periodically to neighbours so as to keep nodes updated on their neighbourhoods. While we cannot do without these overhead packets, they occupy much of the limited wireless bandwidth available in wireless networks. In a reconfigurable wireless ad hoc network scenario, these packets have more negative effects, as links need to be confirmed more frequently than in traditional networks mainly because of the unpredictable behaviour of the ad hoc networks. We therefore need suitable algorithms that will manage these overheads so as to allow data packet to have more access to the wireless medium, save node energy for longer life of the network, increased efficiency, and scalability. Various protocols have been suggested in the research area. They mostly address routing overheads for suitability of particular protocols leading to lack of standardisation and inapplicability to other protocol classes. In this dissertation ways of ensuring that the routing overheads are kept low are investigated. The issue is addressed both at node and network levels with a common goal of improving efficiency and performance of ad hoc networks without dedicating ourselves to a particular class of routing protocol. At node level, a method hereby referred to as "link availability forecast", that minimises routing overheads used for maintenance of neighbourhood, is derived. The targeted packets are packets that are broadcasted periodically (e.g. hello messages). The basic idea in this method is collection of mobility parameters from the neighbours and predictions or forecasts of these parameters in future. Using these parameters in simple calculations helps in identifying link availabilities between nodes participating in maintenance of networks backbone. At the network level, various approaches have been suggested. The first approach is the cone flooding method that broadcasts route request messages through a predetermined cone shaped region. This region is determined through computation using last known mobility parameters of the destination. Another approach is what is hereby referred as "destination search reverse zone method". In this method, a node will keep routes to destinations for a long time and use these routes for tracing the destination. The destination will then initiate route search in a reverse manner, whereby the source selects the best route for next delivery. A modification to this method is for the source node to determine the zone of route search and define the boundaries within which the packet should be broadcasted. The later method has been used for simulation purposes. The protocol used for verification of the improvements offered by the schemes was the AODV. The link availability forecast scheme was implemented on the AODV and labelled AODV_LA while the network level implementation was labelled AODV_RO. A combination of the two schemes was labelled AODV_LARO.

The complex business applications are increasingly offered as services over the Internet, so-called software-as-a-Service (SaaS) applications. The SAP Netweaver Cloud offers an OSGI-based open platform, which enables multi-tenant SaaS applications to run in the cloud. A multi-tenant SaaS application is designed so that an application instance is used by several customers and their users. As different customers have different requirements for functionality and quality of the application, the application instance must be configurable. Therefore, it must be able to add new configurations into a multi-tenant SaaS application at run-time. In this thesis, we proposed concepts of a configuration management, which are used for managing and creating client configurations of cloud applications. The concepts are implemented in a tool that is based on Eclipse and extended feature models. In addition, we evaluate our concepts and the applicability of the developed solution in the SAP Netwaver Cloud by using a cloud application as a concrete case example.:List of Figures i List of Tables iii 1 Introduction 1 1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 The Structure of This Document . . . . . . . . . . . . . . . . . 2 2 Background 5 2.1 Cloud Computing . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 Software Product Line Engineering . . . . . . . . . . . . . . . . 7 2.3 Role Based Access Control . . . . . . . . . . . . . . . . . . . . . 10 2.4 Staged Con guration . . . . . . . . . . . . . . . . . . . . . . . . 12 2.5 Work ow Modeling . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.5.1 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.5.2 Work ow Modeling Languages . . . . . . . . . . . . . . . 16 2.5.3 Adaptive Work ow . . . . . . . . . . . . . . . . . . . . . 17 2.5.4 Adaptation Patterns . . . . . . . . . . . . . . . . . . . . 17 2.6 Graph Transformation . . . . . . . . . . . . . . . . . . . . . . . 18 2.7 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3 Analysis 23 3.1 Illustrative Example . . . . . . . . . . . . . . . . . . . . . . . . 23 3.1.1 Domain and Exiting Platform . . . . . . . . . . . . . . . 24 3.1.2 Yard Management System as a SaaS Application . . . . 28 3.2 Requirements Identi cation . . . . . . . . . . . . . . . . . . . . 28 4 Concept 31 4.1 Con guration Management Speci cation . . . . . . . . . . . . . 31 4.1.1 Variability Modeling . . . . . . . . . . . . . . . . . . . . 32 4.1.2 Stakeholder Views Modeling . . . . . . . . . . . . . . . . 34 4.1.3 Con guration Work ow Modeling . . . . . . . . . . . . . 36 4.2 Con guration Work ow Adaptations . . . . . . . . . . . . . . . 41 4.3 Mapping between Problem Space and Solution Space . . . . . . 47 4.4 Con guration Process Simulation . . . . . . . . . . . . . . . . . 50 5 Implementation 53 5.1 Con guration Speci cation . . . . . . . . . . . . . . . . . . . . . 54 5.1.1 Extended Feature Model Speci cation . . . . . . . . . . 55 5.1.2 View Model Speci cation . . . . . . . . . . . . . . . . . . 56 5.1.3 Con guration Work ow Model Speci cation . . . . . . . 57 5.2 Graph Transformation Rules . . . . . . . . . . . . . . . . . . . . 62 5.3 Mapping Realization . . . . . . . . . . . . . . . . . . . . . . . . 65 5.4 Con guration Management Tooling . . . . . . . . . . . . . . . . 67 5.5 Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 6 Conclusions and Future Work 77 6.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 6.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Bibliography i

Problematisk skolfrånvaro är ett omfattande problem som kan få sociala, emotionella och kunskapsmässiga konsekvenser för barn och ungdomar. Forskning visar att multimodala interventioner är effektiva i att öka skolnärvaro, vilka programstrategier inom interventionerna som fungerar i vilka kontexter saknas däremot kunskap om. En realistisk översikt genomfördes därför i syfte att undersöka vilka orsaker till problematisk skolfrånvaro som går att identifiera i tidigare forskning. Vidare var syftet att öka förståelsen för multimodala interventioner genom att specificera vilka programstrategier som leder till ökad skolnärvaro inom vilka kontexter. Efter en systematisk sökprocess inkluderades totalt 124 vetenskapliga artiklar. Resultatet av den realistiska analysen visade att trygghet, attityd, känsloreglering, social kompetens, motivation, föräldraförmåga, föräldrars föreställningar, kommunikation, tillit, familjedynamik, relationen mellan elev och lärare, skolklimat, skolorganisering, normativa föreställningar samt jämlikhet kan generera skolfrånvaro i särskilda kontexter. Inom de multimodala interventionerna identifierades åtta programstrategier som visat sig öka skolnärvaro i vissa kontexter. Mest empiriskt underlag förelåg för de strategier som arbetade med föräldra-förmågan och kommunikationen i elevens omgivning. Resultatet analyserades med hjälp av behavioristisk teori om operant betingning och systemteori. Översiktens slutsatser kan öka förståelsen för orsaker till skolfrånvaro och vägleda yrkesverksamma i vilka programstrategier som bör implementeras under vilka omständigheter. / Problematic school absenteeism is a comprehensive problem associated with social, emotional and cognitive consequences for children and adolescents. Research shows that multimodal interventions are effective in increasing attendance. However, there is a need to refine the contexts in which multimodal interventions are effective. Therefore, a realistic review was carried out in order to identify the causes underlying problematic school absenteeism in previous research. Furthermore, the purpose was to increase the understanding of multimodal interventions by specifying which program strategies lead to increased school attendance in which contexts. Following a systematic search process, a total of 124 articles were included. The results showed that security, attitude, emotion regulation, social skills, motivation, parent self-efficacy, parental beliefs, communication, trust, family dynamics, student-teacher relationship, school climate, school organization, normative ideas and equality can generate school absenteeism in specific contexts. Eight program strategies that generated attendance in different contexts were identified within the multimodal interventions. Most empirical support were found for the strategies related to parent self-efficacy and communication. The result was analyzed using behavioral and systems theory. The conclusions can advance the understanding of causes to absenteeism and guide professionals regarding which program strategies should be implemented under which circumstances.

Single-atom catalysts (SACs), as promising alternatives to Pt-based catalysts, suffer from the limited choice of center metals and low single-atom loading. Here, we report a pentacoordinated Zr-based SAC with nontrivial axial O ligands (denoted O−Zr−N−C) for oxygen reduction reaction (ORR). The O ligand downshifts the d-band center of Zr and confers Zr sites with stable local structure and proper adsorption capability for intermediates. Consequently, the ORR performance of O−Zr−N−C prominently surpasses that of commercial Pt/C, achieving a half-wave potential of 0.91 V vs. reversible hydrogen electrode and outstanding durability (92 % current retention after 130-hour operation). Moreover, the Zr site shows good resistance towards aggregation, enabling the synthesis of Zr-based SAC with high loading (9.1 wt%). With the high-loading catalyst, the zinc-air battery (ZAB) delivers a record-high power density of 324 mW cm−2 among those of SAC-based ZABs.