Sascha Alda

Towards Composition Management for Component-based Peer-to-Peer Architectures

Recent peer-to-peer architectures do not fulfill the idea of a service-oriented architecture to allow the flexible composition of services towards concrete applications. This can be justified by the absence of flexible notations for the composition of services that incorporate the dynamic nature exposed by peer-to-peer architectures. In this work, the peer-to-peer architecture DeEvolve is presented that provides novel ways for the composition of services including the handling of exceptions such as the failure of peers. The intention of this approach is to facilitate even less-skilled end-users to compose and to maintain service-oriented applications.

Towards Virtual Knowledge Communities in Peer-to-Peer Networks

As a result of the anonymity in todays Web search, it is not possible to receive a personalized search result. Neither prior search results nor search results from other users are taken into consideration. In order to resolve this anonymity towards the search engine, a system is created which locally stores the search results in the scope of a peer-to-peer network. Using the Peer Search Memory (PeerSy) all relevant results are stored and associated with the corresponding queries. By this means, repeated access is facilitated. Furthermore, sharing of associations between queries and relevant results in the peer-to-peer network allows grouping of Virtual Knowledge Communities (VKC) in order to obtain a surplus value in knowledge sharing on the Web.

Cooperative pull-push cycle for searching a hybrid P2P network

Information acquisition is a great challenge in the context of a continually growing Web. Nowadays, large Web search engines are primarily designed to assist an information pull by the user. On this platform, only actual information needs are handled without assistance of long-term needs. To overcome these shortcomings we propose a cooperative system for information pull and push on a peer-to-peer architecture. We present a hybrid network for a collaborative search environment, based on a local personalization strategy on each peer, and a highly-available Web search service (e.g. Google). Each peer participates in the pull-push cycle, and has the function of an information consumer as well as an information provider. Hence, long-term information needs can be identified without any context restrictions, and recommendations are computed based on virtual knowledge communities.

Tailorability of personalized BPEL-based Workflow Compositions

Recent composition languages like BPEL allow for composing single Web Services as higher-level business workflows. Runtime engines obtain the task to deploy and to publish these processes as regular Web services that can be located and used by any client. These runtime engines, however, do not enable end-users to flexibly adapt the constructs that represent a workflow in a personalized manner. The claim of this work is that end-user adaptability (tailorability) of personalized workflows will be increasingly significant for future applications. Based on our experience with component-based tailoring methods, we propose the multi-tier architecture TailorBPEL that supports the tailoring of personalized BPEL-based workflow compositions.

Component-based self-adaptability in peer-to-peer architectures

Current peer-to-peer architectures are hardly resistant against unanticipated exceptions such as the failure of single peers. This can be justified by the absence of sophisticated models for detecting and handling exception in peer-to-peer architectures. On the other hand, existing models for such self-adaptable architectures are rather generic and less practical for end-users. In this work, a component-based self-adaptability model for peer-to-peer architectures is presented that supports end-users in the handling of exceptions during use time. Support is also provided to handle exceptions during deployment and adaptation of an application. All these approaches are integral parts of DeEvolve, a peer-to-peer runtime environment for component-based peer services.

Towards a user-oriented environment for web services composition

Current web services composition engines like ActiveBPEL provide only facilities to create static workflow compositions. Once a workflow is deployed and started, the constructs that represent the workflow cannot be altered subsequently. In fact, only administrator could re-define a workflow at any time. We claim, however, that such an admin-based deployment is not sufficient. For future application scenarios, we see a need for adapting workflow compositions in a personalized manner even at runtime of the deployed workflow. According to this idea, regular end-users should be able to adapt a workflow for accommodating new requirements. Based on our review for the component-based tailoring methods, the paper presents the multi-tier architecture TailorBPEL that supports the tailoring of personalized BPEL-based workflow compositions. We believe that such architecture is significant for having highly flexible and adaptable service-oriented architectures that are considered for the adoption to user-centric application scenarios.

Peer group-based dependency management in service-oriented peer-to-peer architectures

Dependency management in service-Oriented peer-to-Peer architectures aims at handling functional dependencies between a public service hosted by a service providing peer and all consumer peers that rely on that service. The analysis of dependencies on consumer peers is important for supporting the adaptation of a public service. The uncoordinated adaptation of public services potentially leads to malfunctions in the environment of depending peers. In this paper, a novel way for handling service dependencies in peer-to-peer architectures is proposed. This approach suggests that peers of a peer group agree on a common adaptation policy that prescribes how service providing peers have to deal with potential dependencies before an adaptation can be pursued.

Adaptability in component-based peer-to-peer applications

One great challenge in the field of software engineering is to develop reusable, adaptable and scalable software systems. To address this goal, a multiplicity of approaches have been proposed. We present our work towards the realisation of a component model as well as of an architecture serving as a runtime environment for component-based, distributed peer-to-peer applications. We further explain additional concepts for adaptability in peer-to-peer applications.

Strategies for a Component-Based Self-adaptability Model in Peer-to-Peer Architectures

Current peer-to-peer architectures are hardly resistant against unanticipated exceptions such as the failure of single peers. This can be justified by the absence of sophisticated models for exception detection and resolution in peer-to-peer architectures. On the other hand, existing generic models for such self-adaptable architectures are rather theoretical and less suitable for the usage by end-users. In this work, strategies for a new self-adaptability model in peer-to-peer architecture are presented incorporating the component technology as the conceptual foundation. The claim of this approach is that through the intuitive nature of the component technology the process of self-adaptability becomes more applicable and more comprehendible even for less experienced end-users.

Managing Dependencies in Component-Based Distributed Applications

The drift away from monolithic towards distributed, service-oriented application scenarios results in a couple of new challenges concerning the management of these systems. One particular area is the management of dependencies between services. Dependencies can have different appearances, for instance, functional dependencies, semantic integrity conditions, or even dependencies to hardware resources. In this paper we consider services which are provided by software components. The usage of software components promises to allow for flexible and highly tailorable software systems. In the context of our research we consider dependencies in order to enhance the tailorability of component-based, distributed applications. We explain different occurrences of dependencies as well as the necessity of dependency management for adaptations in component-based applications. The paper focuses on a component architecture which allows the deployment of components as well as the management of dependencies between components.