M.J. van Sinderen

Transparent dynamic reconfiguration for CORBA

Distributed systems with high availability requirements have to support some form of dynamic reconfiguration. This means that they must provide the ability to be maintained or upgraded without being taken off-line. Building a distributed system that allows dynamic reconfiguration is very intrusive to the overall design of the system, and generally requires special skills from both the client and server side application developers. There is an opportunity to provide support for dynamic reconfiguration at the object middleware level of distributed systems, and create a dynamic reconfiguration transparency to application developers. We propose a Dynamic Reconfiguration Service for CORBA that allows the reconfiguration of a running system with maximum transparency for both client and server side developers. We describe the architecture, a prototype implementation, and some preliminary test results.

Supporting context-aware mobile applications: an infrastructure approach

Mobile phones and PDAs are converging into mobile lifestyle devices that offer a wide range of applications to end users. Many of these applications will have the ability to adapt themselves to the users situation, commonly referred to as context awareness. We argue that an infrastructure is needed to enable wide deployment of context-aware applications. A major benefit is interoperability between heterogeneous context sources and applications in a privacy-sensitive way. We identify three main technical challenges to realize such an infrastructure: reasoning to infer higher-level and better quality context information; efficient exchange and distributed processing of context information in dynamic and pervasive environments; and end-user-controlled handling of the privacy aspects. This article explains how we address these challenges with regard to the realization of an infrastructure that supports context-aware mobile applications. We use this infrastructure to support several mobile healthcare applications

Mapping the business model canvas to ArchiMate

Many IT projects fail to succeed in the market, as they start purely from technology. Much effort is therefore wasted, while the potential benefits are not realized. We argue that the design process should start with creating a business model, which is then translated to an architecture to ensure fitness for market of the future system. Therefore, we propose a mapping from Osterwalders business modeling canvas and ontology to the enterprise architecture modeling standard ArchiMate, which makes the above translation possible and represents a formal basis for business modeling in ArchiMate. A case study illustrates the mapping between the two languages.

A systematic approach to platform-independent design based on the service concept

This paper aims at demonstrating the benefits and importance of the service concept in the model-driven design of distributed applications. A service defines the observable behaviour of a system without constraining the systems internal structure. We argue that by specifying application-level interaction aspects as a service, and designing application parts is not constrained by interaction patterns provided by a middleware platform. Therefore, a level of platform-independence can be achieved, so that the design of application parts can be reused across a large set of middleware platforms. The service concept is also used in our approach to describe an abstract platform that defines what characteristics of a potential target middleware platform are considered in platform-independent design. We discuss the trade-offs a designer is confronted within the definition of an abstract platform, and discuss alternatives for platform-specific realization.

An approach to relate viewpoints and modeling languages

The architectural design of distributed enterprise applications from the viewpoints of different stakeholders has been proposed for some time, for example, as part of RM-ODP and IEEE 1471, and seems now-a-days to gain acceptance in practice. However, much work remains to be done on the relationships between different viewpoints. Failing to relate viewpoints may lead to a collection of viewpoint models that is inconsistent, and may therefore lead to an incorrect implementation. This paper defines an approach that helps designers to relate different viewpoints to each other. Thereby, it helps to enforce the consistency of the overall design. The results of this paper are expected to be particularly interesting for Model Driven Architecture (MDA) projects, since the proposed models can be used for the explicit definition of the models and relationships between models in an MDA trajectory.

Dependable and Adaptable Networks and Services - Proceedings of the 13th Open European Summer School and IFIP TC6.6 Workshop, EUNICE 2007, Enschede, The Netherlands, July 2007

Technical Session 1: Middleware and Supportive Services.- Identity as a Service - Towards a Service-Oriented Identity Management Architecture.- Towards a Context Binding Transparency.- A Context Middleware Using an Ontology-Based Information Model.- Technical Session 2: Context-Awareness.- Providing Movement Information to Applications in Wireless IPv6 and Mobile IPv6 Terminals.- Towards a Rule-Based Approach for Context-Aware Applications.- Semantic Context Reasoning Using Ontology Based Models.- Technical Session 3: Voice over IP.- VoIP Codec Adaptation Algorithm in Multirate 802.11 WLANs: Distributed vs. Centralized Performance Comparison.- Decentralized Supplementary Services for Voice-over-IP Telephony.- Analysis of Techniques for Protection Against Spam over Internet Telephony.- Technical Session 4: User Behavior, Security and Legal Aspects.- A Reputation-Based Approach for Securing Vivaldi Embedding System.- Source Traffic Characterization for Thin Client Based Office Applications.- Legal Compliance in Commercial Service Provisioning Across Administrative Domains.- Technical Session 5: Performance Aspects.- Measurement of the SIP Parsing Performance in the SIP Express Router.- A Novel Loop-Free IP Fast Reroute Algorithm.- A Simulation-Based Study of TCP Performance over an Optical Burst Switched Backbone with 802.11 Access.- Technical Session 6: Novel Architectures.- Towards Policy-Supported Adaptable Service Systems.- An Architecture for the Self-management of Lambda-Connections in Hybrid Networks.

A component-based groupware development methodology

Software development in general and groupware applications in particular can greatly benefit from the reusability and interoperability aspects associated with software components. Component-based software development enables the construction of software artefacts by assembling prefabricated, configurable and independently evolving buildings blocks, called software components. This paper presents a methodology for the development of groupware applications using a set of composable software components. This methodology consists of splitting the software development process according to four abstraction levels, viz., enterprise, system, component and object, and three different views, viz., structural, behavioural and interactional. The use of different abstraction levels and views allows a better control of the development process. We illustrate this methodology using a chat application as a case study.

Platform-independent dynamic reconfiguration of distributed applications

The aim of dynamic reconfiguration is to allow a system to evolve incrementally from one configuration to another at run-time, without restarting it or taking it offline. In recent years, support for transparent dynamic reconfiguration has been added to middleware platforms, shifting the complexity required to enable dynamic reconfiguration to the supporting infrastructure. These approaches to dynamic reconfiguration are mostly platform-specific and depend on particular implementation approaches suitable for particular platforms. In this paper, we propose an approach to dynamic reconfiguration of distributed applications that is suitable for application implemented on top of different platforms. This approach supports a platform-independent view of an application that profits from reconfiguration transparency. In this view, requirements on the ability to reconfigure components are expressed in an abstract manner. These requirements are then satisfied by platform-specific realizations.

Protocol design and implementation using formal methods

This paper reports on a number of formal methods that support correct protocol design and implementation. These methods are placed in the framework of a design methodology for distributed systems that was studied and developed within the ESPRIT II Lotosphere project (2304). The paper focuses on design methods for synthesizing protocols by successive application of correctness-preserving LOTOS transformations. This transformational approach is described in some detail and is illustrated with a protocol design example. The paper concludes with some suggestions for relating design methods to milestones in the protocol design and implementation processes.

LOTOS specification style for OSI

The architecture of OSI is used to derive guidelines for writing LOTOS specifications of distributed systems. In particular, the architectural concepts that underlie service and protocol designs are examined in detail. For each of these concepts a representation in LOTOS is given. Examples are provided of how the LOTOS representations of the concepts are used in the construction of LOTOS specifications of service and protocol designs. The approach described in this paper is motivated by the need to produce distributed system specifications in a more consistent and productive fashion.