Inconsistency-tolerant Query Answering in Ontology-based Data Access

Ontology-based data access (OBDA) is receiving great attention as a new paradigm for managing information systems through semantic technologies. According to this paradigm, a Description Logic ontology provides an abstract and formal representation of the domain of interest to the information system, and is used as a sophisticated schema for accessing the data and formulating queries over them. In this paper, we address the problem of dealing with inconsistencies in OBDA. Our general goal is both to study DL semantical frameworks that are inconsistency-tolerant, and to devise techniques for answering unions of conjunctive queries under such inconsistency-tolerant semantics. Our work is inspired by the approaches to consistent query answering in databases, which are based on the idea of living with inconsistencies in the database, but trying to obtain only consistent information during query answering, by relying on the notion of database repair. We first adapt the notion of database repair to our context, and show that, according to such a notion, inconsistency-tolerant query answering is intractable, even for very simple DLs. Therefore, we propose a different repair-based semantics, with the goal of reaching a good compromise between the expressive power of the semantics and the computational complexity of inconsistency-tolerant query answering. Indeed, we show that query answering under the new semantics is first-order rewritable in OBDA, even if the ontology is expressed in one of the most expressive members of the DL-Lite family

Inconsistency Handling in Ontology-Mediated Query Answering: A Progress Report

International audienceThis paper accompanies an invited talk on inconsistency handling in OMQA and presents a concise summary of the research that has been conducted in the area

Dealing with Inconsistencies and Updates in Description Logic Knowledge Bases

The main purpose of an "Ontology-based Information System" (OIS) is to provide an explicit description of the domain of interest, called ontology, and let all the functions of the system be based on such representation, thus freeing the users from the knowledge about the physical repositories where the real data reside. The functionalities that an OIS should provide to the user include both query answering, whose goal is to extract information from the system, and update, whose goal is to modify the information content of the system in order to reflect changes in the domain of interest. The "ontology" is a formal, high quality intentional representation of the domain, designed in such a way to avoid inconsistencies in the modeling of concepts and relationships. On the contrary, the extensional level of the system, constituted by a set of autonomous, heterogeneous data sources, is built independently from the conceptualization represented by the ontology, and therefore may contain information that is incoherent with the ontology itself. This dissertation presents a detailed study on the problem of dealing with inconsistencies in OISs, both in query answering, and in performing updates. We concentrate on the case where the knowledge base in the OISs is expressed in Description Logics, especially the logics of the DL-lite family. As for query answering, we propose both semantical frameworks that are inconsistency-tolerant, and techniques for answering unions of conjunctive queries posed to OISs under such inconsistency-tolerant semantics. As for updates, we present an approach to compute the result of updating a possibly inconsistent OIS with both insertion and deletion of extensional knowledge

Practical update management in ontology-based data access

Ontology-based Data Access (OBDA) is gaining importance both scientifically and practically. However, little attention has been paid so far to the problem of updating OBDA systems. This is an essential issue if we want to be able to cope with modifications of data both at the ontology and at the source level, while maintaining the independence of the data sources. In this paper, we propose mechanisms to properly handle updates in this context. We show that updating data both at the ontology and source level is first-order rewritable. We also provide a practical implementation of such updating mechanisms based on non-recursive Datalog.Peer ReviewedPostprint (author's final draft

Maintaining Structured Experiences for Robots via Human Demonstrations: An Architecture To Convey Long-Term Robot\u2019s Beliefs

This PhD thesis presents an architecture for structuring experiences, learned through demonstrations, in a robot memory. To test our architecture, we consider a specific application where a robot learns how objects are spatially arranged in a tabletop scenario. We use this application as a mean to present a few software development guidelines for building architecture for similar scenarios, where a robot is able to interact with a user through a qualitative shared knowledge stored in its memory. In particular, the thesis proposes a novel technique for deploying ontologies in a robotic architecture based on semantic interfaces. To better support those interfaces, it also presents general-purpose tools especially designed for an iterative development process, which is suitable for Human-Robot Interaction scenarios. We considered ourselves at the beginning of the first iteration of the design process, and our objective was to build a flexible architecture through which evaluate different heuristic during further development iterations. Our architecture is based on a novel algorithm performing a oneshot structured learning based on logic formalism. We used a fuzzy ontology for dealing with uncertain environments, and we integrated the algorithm in the architecture based on a specific semantic interface. The algorithm is used for building experience graphs encoded in the robot\u2019s memory that can be used for recognising and associating situations after a knowledge bootstrapping phase. During this phase, a user is supposed to teach and supervise the beliefs of the robot through multimodal, not physical, interactions. We used the algorithm to implement a cognitive like memory involving the encoding, storing, retrieving, consolidating, and forgetting behaviours, and we showed that our flexible design pattern could be used for building architectures where contextualised memories are managed with different purposes, i.e. they contains representation of the same experience encoded with different semantics. The proposed architecture has the main purposes of generating and maintaining knowledge in memory, but it can be directly interfaced with perceiving and acting components if they provide, or require, symbolical knowledge. With the purposes of showing the type of data considered as inputs and outputs in our tests, this thesis also presents components to evaluate point clouds, engage dialogues, perform late data fusion and simulate the search of a target position. Nevertheless, our design pattern is not meant to be coupled only with those components, which indeed have a large room of improvement

IDEAS-1997-2021-Final-Programs

This document records the final program for each of the 26 meetings of the International Database and Engineering Application Symposium from 1997 through 2021. These meetings were organized in various locations on three continents. Most of the papers published during these years are in the digital libraries of IEEE(1997-2007) or ACM(2008-2021)

Natural Language Processing: Emerging Neural Approaches and Applications

This Special Issue highlights the most recent research being carried out in the NLP field to discuss relative open issues, with a particular focus on both emerging approaches for language learning, understanding, production, and grounding interactively or autonomously from data in cognitive and neural systems, as well as on their potential or real applications in different domains

Mining Authoritativeness in Art Historical Photo Archives. Semantic Web Applications for Connoisseurship

The purpose of this work is threefold: (i) to facilitate knowledge discovery in art historical photo archives, (ii) to support users' decision-making process when evaluating contradictory artwork attributions, and (iii) to provide policies for information quality improvement in art historical photo archives. The approach is to leverage Semantic Web technologies in order to aggregate, assess, and recommend the most documented authorship attributions. In particular, findings of this work offer art historians an aid for retrieving relevant sources, assessing textual authoritativeness (i.e. internal grounds) of sources of attribution, and evaluating cognitive authoritativeness of cited scholars. At the same time, the retrieval process allows art historical data providers to define a low-cost data integration process to update and enrich their collection data. The contributions of this thesis are the following: (1) a methodology for representing questionable information by means of ontologies; (2) a conceptual framework of Information Quality measures addressing dimensions of textual and cognitive authoritativeness characterising art historical data, (3) a number of policies for metadata quality improvement in art historical photo archives as derived from the application of the framework, (4) a ranking model leveraging the conceptual framework, (5) a semantic crawler, called mAuth, that harvests authorship attributions in the Web of Data, and (6) an API and a Web Application to serve information to applications and final users for consuming data. Despite findings are limited to a restricted number of photo archives and datasets, the research impacts on a broader number of stakeholders, such as archives, museums, and libraries, which can reuse the conceptual framework for assessing questionable information, mutatis mutandi, to other near fields in the Humanities

Linked open data e ontologie per la descrizione del patrimonio culturale: criteri per la progettazione di un registro ragionato

La tesi affronta il tema del semantic web e della pubblicazione delle informazioni relative al patrimonio culturale in modalità linked open data. In particolare, oggetto dell’attività di ricerca sono i registri di ontologie, vale a dire quegli strumenti che descrivono formalmente i modelli ontologici disponibili sul web e ne agevolano il reperimento e la valutazione, incentivandone il riuso e facilitando i processi di allineamento semantico e di interoperabilità. I registri di ontologie rispondono in modo efficace all’assenza di strumenti di riferimento e di orientamento nei processi di modellazione concettuale delle risorse informative e sono stati sperimentati con successo in diversi domini, ma sono ancora inediti in ambito culturale. L’esame puntuale delle iniziative condotte nell’ultimo decennio nell’ambito dei beni culturali ha evidenziato con chiarezza la mancanza di un assetto epistemologico consolidato nella modellazione concettuale delle risorse informative, a fronte delle numerose ontologie realizzate in funzione dei molteplici progetti di pubblicazione di linked open data. Di conseguenza, risulta tutt’altro che agevole conoscere esaustivamente tutte le ontologie disponibili in relazione al proprio abito di interesse ed ottenere in maniera agevole e sistematica una valutazione attendibile circa la loro capacità rappresentativa e il loro grado di interoperabilità semantica. L’analisi dei principali registri di ontologie finora realizzati al di fuori del dominio dei beni culturali ha consentito di individuare e definire i requisiti di un registro di ontologie per i beni culturali (denominato CLOVER, Culture – Linked Open Vocabularies – Extensible Registry), e di elaborarne la relativa ontologia. L’ontologia ADMS-AP_IT (Asset Description Metadata Schema – Application Profile – Italy) è stata redatta a seguito di un’analisi sistematica e di una valutazione critica di preesistenti ontologie concepite per scopi similari. Essa è stata sottoposta ad AgID, che l’ha inclusa nella rete di ontologie e vocabolari controllati della pubblica amministrazione detta OntoPiA. Tale ontologia rappresenta un punto di arrivo del progetto di ricerca, ma anche una base di partenza per approfondire l'indagine su tali temi: in questo senso, la sua inclusione nella rete OntoPiA di ontologie e vocabolari controllati della pubblica amministrazione si configura come un'opportunità rilevante per sperimentarne l'applicabilità e migliorarne la qualità