Explicitating semantics in Enterprise Information Systems Models

140 pages Report for the Post-Doctorate diploma of the Université Henri Poincaré Supervisors: Hervé Panetto and Alexis AubryInteroperability can be defined as the ability of two or more systems to share, to understand and to consume information (IEEE, 1990). The work (Chen et al., 2006) in the INTEROP NoE project has identified three different levels of barriers for interoperability: technical, conceptual and organisational. Our research focuses on the conceptual level of interoperability, namely the ability to understand the exchanged information. Information may be defined as data linked to knowledge about this data. This research memory will show the results obtained during the Post Doc study referring to the published works. It deals with a first phase from our general research work that focuses on the study of the semantic loss that appears in the exchange of information about business concepts. In order to quantify the semantic gap between interoperating ISs, their semantics needs to be enacted and structured by enriching, normalising and analysing their conceptual models. We propose a conceptualisation approach for explicitation of the finest-grained semantics, embedded into conceptual models in order to facilitate the semantic matching between two different information systems that have to interoperate. The structure of the document represents the different steps and the research domain on which the study focused

An Algebraic Approach to XQuery Optimization

As more data is stored in XML and more applications need to process this data, XML query optimization becomes performance critical. While optimization techniques for relational databases have been developed over the last thirty years, the optimization of XML queries poses new challenges. Query optimizers for XQuery, the standard query language for XML data, need to consider both document order and sequence order. Nevertheless, algebraic optimization proved powerful in query optimizers in relational and object oriented databases. Thus, this dissertation presents an algebraic approach to XQuery optimization. In this thesis, an algebra over sequences is presented that allows for a simple translation of XQuery into this algebra. The formal definitions of the operators in this algebra allow us to reason formally about algebraic optimizations. This thesis leverages the power of this formalism when unnesting nested XQuery expressions. In almost all cases unnesting nested queries in XQuery reduces query execution times from hours to seconds or milliseconds. Moreover, this dissertation presents three basic algebraic patterns of nested queries. For every basic pattern a decision tree is developed to select the most effective unnesting equivalence for a given query. Query unnesting extends the search space that can be considered during cost-based optimization of XQuery. As a result, substantially more efficient query execution plans may be detected. This thesis presents two more important cases where the number of plan alternatives leads to substantially shorter query execution times: join ordering and reordering location steps in path expressions. Our algebraic framework detects cases where document order or sequence order is destroyed. However, state-of-the-art techniques for order optimization in cost-based query optimizers have efficient mechanisms to repair order in these cases. The results obtained for query unnesting and cost-based optimization of XQuery underline the need for an algebraic approach to XQuery optimization for efficient XML query processing. Moreover, they are applicable to optimization in relational databases where order semantics are considered

Rewriting Declarative Query Languages

Queries against databases are formulated in declarative languages. Examples are the relational query language SQL and XPath or XQuery for querying data stored in XML. Using a declarative query language, the querist does not need to know about or decide on anything about the actual strategy a system uses to answer the query. Instead, the system can freely choose among the algorithms it employs to answer a query. Predominantly, query processing in the relational context is accomplished using a relational algebra. To this end, the query is translated into a logical algebra. The algebra consists of logical operators which facilitate the application of various optimization techniques. For example, logical algebra expressions can be rewritten in order to yield more efficient expressions. In order to query XML data, XPath and XQuery have been developed. Both are declarative query languages and, hence, can benefit from powerful optimizations. For instance, they could be evaluated using an algebraic framework. However, in general, the existing approaches are not directly utilizable for XML query processing. This thesis has two goals. The first goal is to overcome the above-mentioned misfits of XML query processing, making it ready for industrial-strength settings. Specifically, we develop an algebraic framework that is designed for the efficient evaluation of XPath and XQuery. To this end, we define an order-aware logical algebra and a translation of XPath into this algebra. Furthermore, based on the resulting algebraic expressions, we present rewrites in order to speed up the execution of such queries. The second goal is to investigate rewriting techniques in the relational context. To this end, we present rewrites based on algebraic equivalences that unnest nested SQL queries with disjunctions. Specifically, we present equivalences for unnesting algebraic expressions with bypass operators to handle disjunctive linking and correlation. Our approach can be applied to quantified table subqueries as well as scalar subqueries. For all our results, we present experiments that demonstrate the effectiveness of the developed approaches

Keyword-Based Querying for the Social Semantic Web

Enabling non-experts to publish data on the web is an important achievement of the social web and one of the primary goals of the social semantic web. Making the data easily accessible in turn has received only little attention, which is problematic from the point of view of incentives: users are likely to be less motivated to participate in the creation of content if the use of this content is mostly reserved to experts. Querying in semantic wikis, for example, is typically realized in terms of full text search over the textual content and a web query language such as SPARQL for the annotations. This approach has two shortcomings that limit the extent to which data can be leveraged by users: combined queries over content and annotations are not possible, and users either are restricted to expressing their query intent using simple but vague keyword queries or have to learn a complex web query language. The work presented in this dissertation investigates a more suitable form of querying for semantic wikis that consolidates two seemingly conflicting characteristics of query languages, ease of use and expressiveness. This work was carried out in the context of the semantic wiki KiWi, but the underlying ideas apply more generally to the social semantic and social web. We begin by defining a simple modular conceptual model for the KiWi wiki that enables rich and expressive knowledge representation. A component of this model are structured tags, an annotation formalism that is simple yet flexible and expressive, and aims at bridging the gap between atomic tags and RDF. The viability of the approach is confirmed by a user study, which finds that structured tags are suitable for quickly annotating evolving knowledge and are perceived well by the users. The main contribution of this dissertation is the design and implementation of KWQL, a query language for semantic wikis. KWQL combines keyword search and web querying to enable querying that scales with user experience and information need: basic queries are easy to express; as the search criteria become more complex, more expertise is needed to formulate the corresponding query. A novel aspect of KWQL is that it combines both paradigms in a bottom-up fashion. It treats neither of the two as an extension to the other, but instead integrates both in one framework. The language allows for rich combined queries of full text, metadata, document structure, and informal to formal semantic annotations. KWilt, the KWQL query engine, provides the full expressive power of first-order queries, but at the same time can evaluate basic queries at almost the speed of the underlying search engine. KWQL is accompanied by the visual query language visKWQL, and an editor that displays both the textual and visual form of the current query and reflects changes to either representation in the other. A user study shows that participants quickly learn to construct KWQL and visKWQL queries, even when given only a short introduction. KWQL allows users to sift the wealth of structure and annotations in an information system for relevant data. If relevant data constitutes a substantial fraction of all data, ranking becomes important. To this end, we propose PEST, a novel ranking method that propagates relevance among structurally related or similarly annotated data. Extensive experiments, including a user study on a real life wiki, show that pest improves the quality of the ranking over a range of existing ranking approaches

Forschungsbericht Universität Mannheim 2006 / 2007

Sie erhalten darin zum einen zusammenfassende Darstellungen zu den Forschungsschwerpunkten und Forschungsprofilen der Universität und deren Entwicklung in der Forschung. Zum anderen gibt der Forschungsbericht einen Überblick über die Publikationen und Forschungsprojekte der Lehrstühle, Professuren und zentralen Forschungseinrichtungen. Diese werden ergänzt um Angaben zur Organisation von Forschungsveranstaltungen, der Mitwirkung in Forschungsausschüssen, einer Übersicht zu den für Forschungszwecke eingeworbenen Drittmitteln, zu den Promotionen und Habilitationen, zu Preisen und Ehrungen und zu Förderern der Universität Mannheim. Darin zeigt sich die Bandbreite und Vielseitigkeit der Forschungsaktivitäten und deren Erfolg auf nationaler und internationaler Ebene

Adaptive anwendungsspezifische Verarbeitung von XML-Dokumenten

In dieser Arbeit wird ein Konzept vorgeschlagen, mit dem neue hohere Operatoren auf der Grundlage existierender Operatoren einer XML-Transformationsprache aufgebaut werden können. Durch das Zusammenfassen von immer wieder auftretenden Operatorkombinationen zu höheren Operatoren können Transformationsdefinitionen bspw. kürzer und verständlicher beschrieben werden. Zur Umsetzung des Konzeptes ist die Ausführungsumgebung XTC entstanden. XTC koordiniert den Ablauf, um höhere Operatoren in niedrigere, letztendlich elementare Operatoren einer Basistransformationssprache zu überführen. Neben XTC wird das Generatorsystem XOpGen entwickelt, welches den Implementierungsaufwand für die neuen höheren Operatoren weiter verringert. Das Potential von höheren Operatoren wird an der vom W3C standardisierten XML-Transformationssprache XSLT demonstriert. XSLT wird mit verschiedenen, sowohl universellen als auch domänenspezifischen, Operatoren erweitert

Skalierbare Ausführung von Prozessanwendungen in dienstorientierten Umgebungen

Die Strukturierung und Nutzung von unternehmensinternen IT-Infrastrukturen auf Grundlage dienstorientierter Architekturen (SOA) und etablierter XML-Technologien ist in den vergangenen Jahren stetig gewachsen. Lag der Fokus anfänglicher SOA-Realisierungen auf der flexiblen Ausführung klassischer, unternehmensrelevanter Geschäftsprozesse, so bilden heutzutage zeitnahe Datenanalysen sowie die Überwachung von geschäftsrelevanten Ereignissen weitere wichtige Anwendungsklassen, um sowohl kurzfristig Probleme des Geschäftsablaufes zu identifizieren als auch um mittel- und langfristige Veränderungen im Markt zu erkennen und die Geschäftsprozesse des Unternehmens flexibel darauf anzupassen. Aufgrund der geschichtlich bedingten, voneinander unabhängigen Entwicklung der drei Anwendungsklassen, werden die jeweiligen Anwendungsprozesse gegenwärtig in eigenständigen Systemen modelliert und ausgeführt. Daraus resultiert jedoch eine Reihe von Nachteilen, welche diese Arbeit aufzeigt und ausführlich diskutiert. Vor diesem Hintergrund beschäftigte sich die vorliegende Arbeit mit der Ableitung einer konsolidierten Ausführungsplattform, die es ermöglicht, Prozesse aller drei Anwendungsklassen gemeinsam zu modellieren und in einer SOA-basierten Infrastruktur effizient auszuführen. Die vorliegende Arbeit adressiert die Probleme einer solchen konsolidierten Ausführungsplattform auf den drei Ebenen der Dienstkommunikation, der Prozessausführung und der optimalen Verteilung von SOA-Komponenten in einer Infrastruktur

WEB recommendations for E-commerce websites

In this part of the thesis we have investigated how the navigation utilizing web recommendations can be implemented on the e-commerce websites based on integrated data sources. The integrated e-commerce websites are an interesting use case for web recommendations. One of the reasons for this interest is that many modern, large and economically successful e-commerce websites follow the integrated approach. Another reason is that especially in the integrated environment, due to the lack of the pre-defined semantic connections between the data, the web recommendations step forward as means of enabling user navigation. In this chapter we have presented the architecture for the websites based on integrated data sources named EC-Fuice. We have also presented the prototypical implementation of our architecture which serves as a proof-of-concept and investigated the challenges of creating navigation on an integrated website. The following issues were addressed in this part of the thesis: Combination of several state-of-the-art tools and techniques in the fields of databases, data integration, ontology matching and web engineering into one generic architecture for creating integrated websites. Comparative experiments with several techniques for instance matching (also known as record linkage or duplicate detection). Investigation on using the ontology matching to facilitate the instance matching. Comparative experiments with several techniques for ontology matching. Investigations on the instance-based ontology matching and the possibilities for combining instance-based ontology matching with other techniques for ontology matching. Investigation of the possibilities to improve user navigation in the integrated data environment with different types of web recommendations. Review of the related work in the fields of data integration and ontology matching and discussion of the contact points between the research described here and other related projects. The main contributions of the research described in this part of the thesis are the EC-Fuice architecture, the novel method for matching e-commerce ontologies based on combination of instance information and metadata information, the experimental results of ontology and instance matching performed by different matching algorithms and the classification of the types of recommendations which can be used on an integrated e-commerce website

Forschungsbericht Universität Mannheim, 2004 / 2005

Die Universität Mannheim gibt in dem vorliegenden Forschungsbericht 2004/2005 Rechenschaft über ihre Leistungen auf dem Gebiet der Forschung. Erstmals folgt diese Dokumentation einer neuen Gliederung, die auf einen Beschluss des Forschungsrates der Universität Mannheim zurückgeht. Wie gewohnt erhalten Sie einen Überblick über die Publikationen und Forschungsprojekte der Lehrstühle, Professuren und zentralen Forschungseinrichtungen. Diese werden ergänzt um Angaben zur Organisation von Forschungsveranstaltungen, der Mitwirkung in Forschungsausschüssen, einer Übersicht zu den für Forschungszwecke eingeworbenen Drittmitteln, zu den Promotionen und Habilitationen, zu Preisen und Ehrungen und zu Förderern der Universität Mannheim. Abgerundet werden diese Daten durch zusammenfassende Darstellungen der Forschungsschwerpunkte und des Forschungsprofils der Fakultäten