Semantic search and composition in unstructured peer-to-peer networks

This dissertation focuses on several research questions in the area of semantic search and composition in unstructured peer-to-peer (P2P) networks. Going beyond the state of the art, the proposed semantic-based search strategy S2P2P offers a novel path-suggestion based query routing mechanism, providing a reasonable tradeoff between search performance and network traffic overhead. In addition, the first semantic-based data replication scheme DSDR is proposed. It enables peers to use semantic information to select replica numbers and target peers to address predicted future demands. With DSDR, k-random search can achieve better precision and recall than it can with a near-optimal non-semantic replication strategy. Further, this thesis introduces a functional automatic semantic service composition method, SPSC. Distinctively, it enables peers to jointly compose complex workflows with high cumulative recall but low network traffic overhead, using heuristic-based bidirectional haining and service memorization mechanisms. Its query branching method helps to handle dead-ends in a pruned search space. SPSC is proved to be sound and a lower bound of is completeness is given. Finally, this thesis presents iRep3D for semantic-index based 3D scene selection in P2P search. Its efficient retrieval scales to answer hybrid queries involving conceptual, functional and geometric aspects. iRep3D outperforms previous representative efforts in terms of search precision and efficiency.Diese Dissertation bearbeitet Forschungsfragen zur semantischen Suche und Komposition in unstrukturierten Peer-to-Peer Netzen(P2P). Die semantische Suchstrategie S2P2P verwendet eine neuartige Methode zur Anfrageweiterleitung basierend auf Pfadvorschlägen, welche den Stand der Wissenschaft übertrifft. Sie bietet angemessene Balance zwischen Suchleistung und Kommunikationsbelastung im Netzwerk. Außerdem wird das erste semantische System zur Datenreplikation genannt DSDR vorgestellt, welche semantische Informationen berücksichtigt vorhergesagten zukünftigen Bedarf optimal im P2P zu decken. Hierdurch erzielt k-random-Suche bessere Präzision und Ausbeute als mit nahezu optimaler nicht-semantischer Replikation. SPSC, ein automatisches Verfahren zur funktional korrekten Komposition semantischer Dienste, ermöglicht es Peers, gemeinsam komplexe Ablaufpläne zu komponieren. Mechanismen zur heuristischen bidirektionalen Verkettung und Rückstellung von Diensten ermöglichen hohe Ausbeute bei geringer Belastung des Netzes. Eine Methode zur Anfrageverzweigung vermeidet das Feststecken in Sackgassen im beschnittenen Suchraum. Beweise zur Korrektheit und unteren Schranke der Vollständigkeit von SPSC sind gegeben. iRep3D ist ein neuer semantischer Selektionsmechanismus für 3D-Modelle in P2P. iRep3D beantwortet effizient hybride Anfragen unter Berücksichtigung konzeptioneller, funktionaler und geometrischer Aspekte. Der Ansatz übertrifft vorherige Arbeiten bezüglich Präzision und Effizienz

Designing the domestic Internet of Things using a practice-orientated perspective

The Internet of Things (IoT) is a system of sensing, actuating and networked objects, often discussed as delivering efficiency through machine determined, automated decision making and action to achieve ‘Smartness’ in a logistically based paradigm. When applied to the domestic space these values are touted as beneficially controlling lighting, heating and entertainment to improve efficiency and comfort, while reducing costs. This approach follows the external goods of effectiveness, reducing everything to an objective value/cost proposition; however, the home is a subjectively experienced space incorporating differing values, so this reductive perspective overlooks a wider spectrum of inhabitant’s concerns relating to their daily activities and the domestic space. Furthermore, this approach can supplant involvement in domestic activities by treating these as computable problems to solve, alienating users through automation, a lack of transparency and poor understanding of the reasoning behind machine decision making. Existing attempts to address this topic indicate Techno-Centric approaches impact on understanding and engagement with the domestic space; Human-Centric perspectives focus on supporting people’s subjective experiences by prioritising their activities, sense-making and sensory experiences within the design process; Beyond Human-Centric IoT perspectives broaden this understanding to propose non-hierarchical, flat ontologies for the IoT and the implications this has on integrating human/non-human agency in the IoT, generally and domestically. This supported an approach utilising Practice Theory, a development of organising concepts for theorising social life, with sociality dependent on activities conducted with materials to develop a coherent sense of self and which understands place as a meshwork of human/non-human agency. Practice Theory is applied within a Design Research approach using a synergistic Participatory Action Research (PAR) / Participatory Design (PD) process. Exploring Domestic Practices contextualised the IoT through a range of methods including interactive installations, interviews and design workshops, uncovering participant attitudes towards the IoT, generating Practice Themes and specific examples of practices and constituent elements. These acted as User Generated Values (UGV) in a Values-Led PD process to inform the project pathway and the conceptualisation of a Practice-Oriented IoT through PAR’s Action-Reflection spirals. Additionally, a parallel PD process explored the effective communication of UGV within Professional Design Practice (PDP) workshops with the intent of reducing communicative distance between end-users and developers, supporting communication of user’s attitudes towards the IoT and Practice within PDP through inclusion as guiding values. Models of the IoT balancing Practice and technical concerns, workshops and toolkit were developed iteratively, leading to an outcome modelling the IoT and Practice within a flat ontology. Through this, and by embedding Practice within the IoT itself, IoT agency was reframed from automation towards assistiveness in Practice and IoT values shifted from efficiency in external goods of effectiveness towards internally derived goods of excellence, supporting skill development, engagement and reflection on action. This identifies the value of using PAR and PD to consider people’s values, goals and existing practices when developing the domestic IoT. This was particularly valuable in exploring Practice to understand people’s activities in the home and contextualise attitudes towards the IoT. This informed the development of a framework balancing the IoT’s technological nature with people’s activities and values, a system guided by Practice elements reciprocally informing and supporting participant engagement in dynamically developing domestic practices