Ontology mapping: the state of the art

Ontology mapping is seen as a solution provider in today's landscape of ontology research. As the number of ontologies that are made publicly available and accessible on the Web increases steadily, so does the need for applications to use them. A single ontology is no longer enough to support the tasks envisaged by a distributed environment like the Semantic Web. Multiple ontologies need to be accessed from several applications. Mapping could provide a common layer from which several ontologies could be accessed and hence could exchange information in semantically sound manners. Developing such mapping has beeb the focus of a variety of works originating from diverse communities over a number of years. In this article we comprehensively review and present these works. We also provide insights on the pragmatics of ontology mapping and elaborate on a theoretical approach for defining ontology mapping

Ontology Mapping: The State of the Art

Ontology mapping is seen as a solution provider in today\u27s landscape of ontology research. As the number of ontologies that are made publicly available and accessible on the Web increases steadily, so does the need for applications to use them. A single ontology is no longer enough to support the tasks envisaged by a distributed environment like the Semantic Web. Multiple ontologies need to be accessed from several applications. Mapping could provide a common layer from which several ontologies could be accessed and hence could exchange information in semantically sound manners. Developing such mapping has beeb the focus of a variety of works originating from diverse communities over a number of years. In this article we comprehensively review and present these works. We also provide insights on the pragmatics of ontology mapping and elaborate on a theoretical approach for defining ontology mapping

Metadata-driven data integration

Cotutela: Universitat Politècnica de Catalunya i Université Libre de Bruxelles, IT4BI-DC programme for the joint Ph.D. degree in computer science.Data has an undoubtable impact on society. Storing and processing large amounts of available data is currently one of the key success factors for an organization. Nonetheless, we are recently witnessing a change represented by huge and heterogeneous amounts of data. Indeed, 90% of the data in the world has been generated in the last two years. Thus, in order to carry on these data exploitation tasks, organizations must first perform data integration combining data from multiple sources to yield a unified view over them. Yet, the integration of massive and heterogeneous amounts of data requires revisiting the traditional integration assumptions to cope with the new requirements posed by such data-intensive settings. This PhD thesis aims to provide a novel framework for data integration in the context of data-intensive ecosystems, which entails dealing with vast amounts of heterogeneous data, from multiple sources and in their original format. To this end, we advocate for an integration process consisting of sequential activities governed by a semantic layer, implemented via a shared repository of metadata. From an stewardship perspective, this activities are the deployment of a data integration architecture, followed by the population of such shared metadata. From a data consumption perspective, the activities are virtual and materialized data integration, the former an exploratory task and the latter a consolidation one. Following the proposed framework, we focus on providing contributions to each of the four activities. We begin proposing a software reference architecture for semantic-aware data-intensive systems. Such architecture serves as a blueprint to deploy a stack of systems, its core being the metadata repository. Next, we propose a graph-based metadata model as formalism for metadata management. We focus on supporting schema and data source evolution, a predominant factor on the heterogeneous sources at hand. For virtual integration, we propose query rewriting algorithms that rely on the previously proposed metadata model. We additionally consider semantic heterogeneities in the data sources, which the proposed algorithms are capable of automatically resolving. Finally, the thesis focuses on the materialized integration activity, and to this end, proposes a method to select intermediate results to materialize in data-intensive flows. Overall, the results of this thesis serve as contribution to the field of data integration in contemporary data-intensive ecosystems.Les dades tenen un impacte indubtable en la societat. La capacitat d’emmagatzemar i processar grans quantitats de dades disponibles és avui en dia un dels factors claus per l’èxit d’una organització. No obstant, avui en dia estem presenciant un canvi representat per grans volums de dades heterogenis. En efecte, el 90% de les dades mundials han sigut generades en els últims dos anys. Per tal de dur a terme aquestes tasques d’explotació de dades, les organitzacions primer han de realitzar una integració de les dades, combinantles a partir de diferents fonts amb l’objectiu de tenir-ne una vista unificada d’elles. Per això, aquest fet requereix reconsiderar les assumpcions tradicionals en integració amb l’objectiu de lidiar amb els requisits imposats per aquests sistemes de tractament massiu de dades. Aquesta tesi doctoral té com a objectiu proporcional un nou marc de treball per a la integració de dades en el context de sistemes de tractament massiu de dades, el qual implica lidiar amb una gran quantitat de dades heterogènies, provinents de múltiples fonts i en el seu format original. Per això, proposem un procés d’integració compost d’una seqüència d’activitats governades per una capa semàntica, la qual és implementada a partir d’un repositori de metadades compartides. Des d’una perspectiva d’administració, aquestes activitats són el desplegament d’una arquitectura d’integració de dades, seguit per la inserció d’aquestes metadades compartides. Des d’una perspectiva de consum de dades, les activitats són la integració virtual i materialització de les dades, la primera sent una tasca exploratòria i la segona una de consolidació. Seguint el marc de treball proposat, ens centrem en proporcionar contribucions a cada una de les quatre activitats. La tesi inicia proposant una arquitectura de referència de software per a sistemes de tractament massiu de dades amb coneixement semàntic. Aquesta arquitectura serveix com a planell per a desplegar un conjunt de sistemes, sent el repositori de metadades al seu nucli. Posteriorment, proposem un model basat en grafs per a la gestió de metadades. Concretament, ens centrem en donar suport a l’evolució d’esquemes i fonts de dades, un dels factors predominants en les fonts de dades heterogènies considerades. Per a l’integració virtual, proposem algorismes de rescriptura de consultes que usen el model de metadades previament proposat. Com a afegitó, considerem heterogeneïtat semàntica en les fonts de dades, les quals els algorismes de rescriptura poden resoldre automàticament. Finalment, la tesi es centra en l’activitat d’integració materialitzada. Per això proposa un mètode per a seleccionar els resultats intermedis a materialitzar un fluxes de tractament intensiu de dades. En general, els resultats d’aquesta tesi serveixen com a contribució al camp d’integració de dades en els ecosistemes de tractament massiu de dades contemporanisLes données ont un impact indéniable sur la société. Le stockage et le traitement de grandes quantités de données disponibles constituent actuellement l’un des facteurs clés de succès d’une entreprise. Néanmoins, nous assistons récemment à un changement représenté par des quantités de données massives et hétérogènes. En effet, 90% des données dans le monde ont été générées au cours des deux dernières années. Ainsi, pour mener à bien ces tâches d’exploitation des données, les organisations doivent d’abord réaliser une intégration des données en combinant des données provenant de sources multiples pour obtenir une vue unifiée de ces dernières. Cependant, l’intégration de quantités de données massives et hétérogènes nécessite de revoir les hypothèses d’intégration traditionnelles afin de faire face aux nouvelles exigences posées par les systèmes de gestion de données massives. Cette thèse de doctorat a pour objectif de fournir un nouveau cadre pour l’intégration de données dans le contexte d’écosystèmes à forte intensité de données, ce qui implique de traiter de grandes quantités de données hétérogènes, provenant de sources multiples et dans leur format d’origine. À cette fin, nous préconisons un processus d’intégration constitué d’activités séquentielles régies par une couche sémantique, mise en oeuvre via un dépôt partagé de métadonnées. Du point de vue de la gestion, ces activités consistent à déployer une architecture d’intégration de données, suivies de la population de métadonnées partagées. Du point de vue de la consommation de données, les activités sont l’intégration de données virtuelle et matérialisée, la première étant une tâche exploratoire et la seconde, une tâche de consolidation. Conformément au cadre proposé, nous nous attachons à fournir des contributions à chacune des quatre activités. Nous commençons par proposer une architecture logicielle de référence pour les systèmes de gestion de données massives et à connaissance sémantique. Une telle architecture consiste en un schéma directeur pour le déploiement d’une pile de systèmes, le dépôt de métadonnées étant son composant principal. Ensuite, nous proposons un modèle de métadonnées basé sur des graphes comme formalisme pour la gestion des métadonnées. Nous mettons l’accent sur la prise en charge de l’évolution des schémas et des sources de données, facteur prédominant des sources hétérogènes sous-jacentes. Pour l’intégration virtuelle, nous proposons des algorithmes de réécriture de requêtes qui s’appuient sur le modèle de métadonnées proposé précédemment. Nous considérons en outre les hétérogénéités sémantiques dans les sources de données, que les algorithmes proposés sont capables de résoudre automatiquement. Enfin, la thèse se concentre sur l’activité d’intégration matérialisée et propose à cette fin une méthode de sélection de résultats intermédiaires à matérialiser dans des flux des données massives. Dans l’ensemble, les résultats de cette thèse constituent une contribution au domaine de l’intégration des données dans les écosystèmes contemporains de gestion de données massivesPostprint (published version

Essential Difficulty: Faith, Secularity and Transformation

The recent phenomenon of Christian interest litigations instantiates a wider difficulty. This difficulty involves the theological political problems of secularity and religious identity, as these find expression in the everyday aporiae of practiced Christian religious conviction. The core argument of the thesis is that these problems need to be understood and dealt with as difficult. It asks what resources can help articulate these problems, and their difficulty, as a feature of late-modern Western democracies, but without sliding into forms of culture war. Oliver O’Donovan and John Milbank are two key figures for political theology, but their work tends to set Christianity in an oppositional relationship to secular late modernity. The thesis argues that some contrasting but key decisions in their theology mean that they do not deal with the aporiae of that relationship. Rowan Williams is the key conversation partner in the thesis. He uses the notion of ‘difficulty’ frequently but enigmatically in his theology, including his political theology. The thesis undertakes a sustained engagement with Williams over two chapters, to propose that his understanding and use of the notion of difficulty produces an account of political action as an invitational and dispossessive negotiation of difference. The thesis suggests that Williams’s concept of difficulty offers a means for critical, dialogical engagement with secular perspectives and commitments from a position of Christian faith. It provides resources for faithfully negotiating Western political settings, particularly in the context of everyday aporiae, in ways which are potentially transformative but ultimately without guarantees

A critical assessment of the metropolitan police mandate within a constitutional democratic framework : the case of Gauteng metropolitan police departments

Text in English, with summaries in English, Xhosa and ZuluThis research was directed towards investigating if the metropolitan police mandate, as it is collectively perceived by senior metropolitan police officials in Gauteng, is constructive and aligned to the notion of a democratic South Africa. Qualitative data was collected from all metropolitan police departments in Gauteng through an extensive series of semi structured interviews. By adopting a phenomenographic research approach, collected data was transcribed, analysed and hierarchically arranged into a variety of qualitatively different but intrinsically related categories of description. From these categories of description, multiple collective understandings relating to democracy in South Africa, democratic policing and the metropolitan police role emerged. Further analysis revealed that the senior metropolitan police managers collectively fosters a significantly limited understanding of democracy, predominantly based on rudimentary and general democratic principles and values. The collective understanding participants held in relation to democratic policing was also significantly rudimentary and limited, as it principally revolved around the notion of police accountability. Again, the absence of an explicit relationship between participants and South Africa’s democracy was notable. Sequentially, it emerged that participants predominantly do not understand or perceive the metropolitan police department or its mandate as is appropriate within the framework of South Africa’s constitutional democracy. The democratic features of a preventative and proactive focus, objective professionalism and individual and situational responsiveness are thus remarkably absent from these departments. Subsequently, the metropolitan police mandate, as it is collectively perceived by senior metropolitan police officials in the Gauteng Province, is neither appropriate nor constructive to a democratic South Africa.Olu phando lwalujoliswe ekuphandeni ukuba ingaba igunya lamapolisa esixeko, njengoko libonwa njalo ngawo wonke amagosa aphezulu obupolisa besixeko eGauteng, liyakha kwaye lingqamene na nombono woMzantsi Afrika wedemokhrasi. Kwaqokelelwa iinkcukacha zolwazi lomgangatho kuwo wonke amasebe amapolisa esixeko eGauteng, oko kusenziwa ngothotho lodliwano ndlebe olunzulu nolungaqingqwanga ncam. Kwasetyenziswa indlela yophando ejonga iimeko ngobunjalo bazo, iinkcukacha zolwazi ezaqokelelwayo zahlalutywa zacwangciswa ngokwamanqwanqwa olandelelwano, zangamaqela enkcazelo aneempawu ezingafaniyo nangona zizalana. Ukususela kula maqela enkcazelo kwaqondakala iqela lezimvo eziphathelene nedemokhrasi eMzantsi Afrika, ukugcina umthetho ngokwedemokhrasi kwaze kwavela indima yamapolisa esixeko. Uhlalutyo lwaqhuba lwavelisa ukuba abaphathi bamapolisa esixeko ewonke abonakalisa ukungayiqondi kakuhle idemokhrasi, ikakhulu asekeleze iinqobo ezingacolekanga zedemokhrasi. Uluvo lwabo bonke abathathi nxaxheba xa luthelekiswa nokugcina umthetho ngokwedemokhrasi lwafumaniseka ukuba nalo alucolekanga ngaye lulwazana oluncinci, kuba lwalungqonge ingcinga yokuba amapolisa amele izenzo zawo. Ngaphezu koko, kwaqapheleka ukungabikho kobudlelwane phakathi kwabathathi nxaxheba nedemokhrasi yoMzantsi Afrika. Okulandelayo yaba kukuqaphela ukuba abathathi nxaxheba abaliqondi iSebe okanye igunya lamapolisa esixeko njengoko libekiwe kwisakhelo sedemokhrasi yoMgaqo Siseko yoMzantsi Afrika. Azikho kwaphela kula maSebe iimpawu zedemokhrasi zokuthintela nokulungiselela kungekaqhambuki bubi, ukusebenza kakuhle nokuvelela izinto macala onke kwanokukwazi ukusabela kwimeko ethile. Ngoko ke, igunya lamapolisa esixeko, njengoko libonwa njalo ngawo wonke amagosa aphezulu amapolisa esixeko kwiPhondo iGauteng, alifanelekanga kwaye aliwakhi uMzantsi Afrika wedemokhrasi.Lolu cwaningo lwaluqondiswe ekuhloleni ukuthi isijubo samaphoyisa edolobhakazi, ngendlela esibonwa ngayo yizikhulu zasemaphoyiseni edolobhakazi eGauteng singesakhayo na nokuthi siyahambisana yini nombono weNingizimu Afrika yentando yeningi. Imininingwane yocwaningo emayelana namaqiniso yaqoqwa kuyo yonke iminyango yamaphoyisa edolobhakazi eGauteng ngokusebenzisa uchungechunge olubanzi lwezingxoxo ezihleliwe. Ngokulandela indlela yocwaningo ebheka ukuthi abantu bacabangani noma bayithola injani into ethile, imininingwane eqoqiwe yashicilelwa yaba ngumbhalo, yahlaziywa yabe seyihlelwa ngokulandelana kokukhula kwayo yaba yizinhlobonhlobo zemikhakha yencazelo engamazingahle ahlukahlukene kodwa futhi zibe zihlobene ngokwemvelo. Kule mikhakha yencazelo, kuvele ukuqonda okwahlukene kaningi eqoqweni elilodwa ngokufanayo maqondana nentando yeningi eNingizimu Afrika, ukuqapha okuhambisana nentando yeningi kanye nendima edlalwa ngamaphoyisa edolobhakazi. Olunye uhlaziyo luveze ukuthi izikhulu zasemaphoyiseni edolobhakazi, ngokuhlanganyela, zinokuqonda okunomkhawulo maqondana nentando yeningi, ikakhulukazi kokuphathelene nemigomo nezimiso ezejwayelekile zentando yeningi. Ukuqonda kweqoqo lababambiqhaza ngokuhlanganyela maqondana nokuqapha okuhambisana nentando yeningi nakho kwaba ngokwejwayeleke kakhulu futhi kwaba nomkhawulo, njengoba kwakugxile kakhulu embonweni wokuziphedulela kwamaphoyisa. Kanti okunye, ukungabi khona kobudlelwano obucacile phakathi kwababambiqhaza kanye nentando yeningi yeNingizimu Afrika nakho kwabonakala. Okwalandela lapho kwaba ngukuthi ababambiqhaza abaningi abaqondi kahle kumbe babona umnyango wamaphoyisa edolobhakazi noma isijubo sawo njengefanelekile ngokohlaka lwentando yeningi yeNingizimu Afrika elandela umthethosisekelo. Ngakho-ke, izinto ezihambisana nentando yeningi maqondana nokugxila ekuvimbeleni nasekwenzeni izinto ngaphandle kokutshelwa, ukuqeqesheka kahle ngokubheka wonke amacala kanye nokubhekana nezinto eziqondene nomuntu ngamunye noma nezimo, azitholakali kule minyango. Ngenxa yalokho, isijubo samaphoyisa edolobhakazi, ngendlela esibonwa ngayo yizikhulu zasemaphoyiseni edolobhakazi esifundazweni saseGauteng, singesingafanelekile nesingakhi eNingizimu Afrika yentando yeningi.Police PracticeD. Lit. et Phil. (Police Science

Ontologies for Legal Relevance and Consumer Complaints. A Case Study in the Air Transport Passenger Domain

Applying relevant legal information to settle complaints and disputes is a common challenge for all legal practitioners and laymen. However, the analysis of the concept of relevance itself has thus far attracted only sporadic attention. This thesis bridges this gap by understanding the components of complaints, and by defining relevant legal information, and makes use of computational ontologies and design patterns to represent this relevant knowledge in an explicit and structured way. This work uses as a case-study a real situation of consumer disputes in the Air Transport Passenger domain. Two artifacts were built: the Relevant Legal Information in Consumer Disputes Ontology, and its specialization, the Air Transport Passenger Incidents Ontology, aimed at modelling relevant legal information; and the Complaint Design Pattern proposed to conceptualize complaints. In order to demonstrate the ability of the ontologies to serve as a knowledge base for a computer program providing relevant legal information, a demonstrative application was developed

Structural Summaries as a Core Technology for Efficient XML Retrieval

The Extensible Markup Language (XML) is extremely popular as a generic markup language for text documents with an explicit hierarchical structure. The different types of XML data found in today’s document repositories, digital libraries, intranets and on the web range from flat text with little meaningful structure to be queried, over truly semistructured data with a rich and often irregular structure, to rather rigidly structured documents with little text that would also fit a relational database system (RDBS). Not surprisingly, various ways of storing and retrieving XML data have been investigated, including native XML systems, relational engines based on RDBSs, and hybrid combinations thereof. Over the years a number of native XML indexing techniques have emerged, the most important ones being structure indices and labelling schemes. Structure indices represent the document schema (i.e., the hierarchy of nested tags that occur in the documents) in a compact central data structure so that structural query constraints (e.g., path or tree patterns) can be efficiently matched without accessing the documents. Labelling schemes specify ways to assign unique identifiers, or labels, to the document nodes so that specific relations (e.g., parent/child) between individual nodes can be inferred from their labels alone in a decentralized manner, again without accessing the documents themselves. Since both structure indices and labelling schemes provide compact approximate views on the document structure, we collectively refer to them as structural summaries. This work presents new structural summaries that enable highly efficient and scalable XML retrieval in native, relational and hybrid systems. The key contribution of our approach is threefold. (1) We introduce BIRD, a very efficient and expressive labelling scheme for XML, and the CADG, a combined text and structure index, and combine them as two complementary building blocks of the same XML retrieval system. (2) We propose a purely relational variant of BIRD and the CADG, called RCADG, that is extremely fast and scales up to large document collections. (3) We present the RCADG Cache, a hybrid system that enhances the RCADG with incremental query evaluation based on cached results of earlier queries. The RCADG Cache exploits schema information in the RCADG to detect cached query results that can supply some or all matches to a new query with little or no computational and I/O effort. A main-memory cache index ensures that reusable query results are quickly retrieved even in a huge cache. Our work shows that structural summaries significantly improve the efficiency and scalability of XML retrieval systems in several ways. Former relational approaches have largely ignored structural summaries. The RCADG shows that these native indexing techniques are equally effective for XML retrieval in RDBSs. BIRD, unlike some other labelling schemes, achieves high retrieval performance with a fairly modest storage overhead. To the best of our knowledge, the RCADG Cache is the only approach to take advantage of structural summaries for effectively detecting query containment or overlap. Moreover, no other XML cache we know of exploits intermediate results that are produced as a by-product during the evaluation from scratch. These are valuable cache contents that increase the effectiveness of the cache at no extra computational cost. Extensive experiments quantify the practical benefit of all of the proposed techniques, which amounts to a performance gain of several orders of magnitude compared to various other approaches

A framework for information integration using ontological foundations

With the increasing amount of data, ability to integrate information has always been a competitive advantage in information management. Semantic heterogeneity reconciliation is an important challenge of many information interoperability applications such as data exchange and data integration. In spite of a large amount of research in this area, the lack of theoretical foundations behind semantic heterogeneity reconciliation techniques has resulted in many ad-hoc approaches. In this thesis, I address this issue by providing ontological foundations for semantic heterogeneity reconciliation in information integration. In particular, I investigate fundamental semantic relations between properties from an ontological point of view and show how one of the basic and natural relations between properties – inferring implicit properties from existing properties – can be used to enhance information integration. These ontological foundations have been exploited in four aspects of information integration. First, I propose novel algorithms for semantic enrichment of schema mappings. Second, using correspondences between similar properties at different levels of abstraction, I propose a configurable data integration system, in which query rewriting techniques allows the tradeoff between accuracy and completeness in query answering. Third, to keep the semantics in data exchange, I propose an entity preserving data exchange approach that reflects source entities in the target independent of classification of entities. Finally, to improve the efficiency of the data exchange approach proposed in this thesis, I propose an extended model of the column-store model called sliced column store. Working prototypes of the techniques proposed in this thesis are implemented to show the feasibility of realizing these techniques. Experiments that have been performed using various datasets show the techniques proposed in this thesis outperform many existing techniques in terms of ability to handle semantic heterogeneities and performance of information exchange

An institutional and relational approach to social accountability: lessons from two Colombian cities

Social accountability is considered a key democratic feature that can help to secure responsiveness, service delivery and control power-holders. The thesis responds to how may social accountability be secured in weak democratic contexts through three sub-questions: First, to what extent do public officials align with the role of 'account-givers' and societal actors that of 'account-holders'? Second, how may societal actors assess the performance of public officials? And third, how may societal actors impose consequences on public officials, and public officials respond? The thesis draws on recent studies analysing social accountability beyond mechanisms and is interested in how context matters for the success of such initiatives and how political history and other structures shape the interactions between state and society. This research contributes to this body of literature by employing a relational and institutional approach, analysing social accountability as an institution. The thesis explores the set of rules, practices and narratives interacting with officials and societal actors and creating regular patterns of (un)accountable behaviour such as monitoring, access to information, justifications, deliberation and possibly imposing sanctions, rewards and call or provision of redress. The research is based on a case study focusing on two Colombian cities where social accountability is expected to emerge given traditional accountability deficits, corruption, and insufficient provision of services. The findings are drawn from 40 semi-structured interviews, documentary analysis and observation of public hearings. The study suggests that a dyadic relational approach may overlook civil society organisations as intermediaries between public officials and citizens and the significance of such a role in social accountability institutionalisation. The thesis also uncovers the tensions between institutional stability and weakening and argues they can be explained by the interaction with other institutions, such as exclusionary bipartisanism, clientelism and decentralisation. While exclusionary bipartisanism and clientelism create incentives for ‘window dressing’, decentralisation within cities can complement social accountability arrangements. These institutional dynamics underpin gaps between institutional arrangements hindering social accountability and further reinforcing power asymmetries between public officials or political elite and citizens, especially those facing critical socioeconomic challenges. While rules prescribe ongoing interactions, in practice, social accountability is reduced to specific events where local governments exercise power and control and portray narratives of compliance and responsiveness. Simultaneously, societal actors’ ability to participate and impose consequences is limited but some resist and push forward changes, contributing to understanding the importance of analysing multiple actors’ behaviours and how they shape institutions