Knowledge Propagation in Contextualized Knowledge Repositories: an Experimental Evaluation

As the interest in the representation of context dependent knowledge in the Semantic Web has been recognized, a number of logic based solutions have been proposed in this regard. In our recent works, in response to this need, we presented the description logic-based Contextualized Knowledge Repository (CKR) framework. CKR is not only a theoretical framework, but it has been effectively implemented over state-of-the-art tools for the management of Semantic Web data: inference inside and across contexts has been realized in the form of forward SPARQL-based rules over different RDF named graphs. In this paper we present the first evaluation results for such CKR implementation. In particular, in first experiment we study its scalability with respect to different reasoning regimes. In a second experiment we analyze the effects of knowledge propagation on the computation of inferences.Comment: ARCOE-Logic 2014 Workshop Notes, pp. 13-2

Pseudo-contractions as Gentle Repairs

Updating a knowledge base to remove an unwanted consequence is a challenging task. Some of the original sentences must be either deleted or weakened in such a way that the sentence to be removed is no longer entailed by the resulting set. On the other hand, it is desirable that the existing knowledge be preserved as much as possible, minimising the loss of information. Several approaches to this problem can be found in the literature. In particular, when the knowledge is represented by an ontology, two different families of frameworks have been developed in the literature in the past decades with numerous ideas in common but with little interaction between the communities: applications of AGM-like Belief Change and justification-based Ontology Repair. In this paper, we investigate the relationship between pseudo-contraction operations and gentle repairs. Both aim to avoid the complete deletion of sentences when replacing them with weaker versions is enough to prevent the entailment of the unwanted formula. We show the correspondence between concepts on both sides and investigate under which conditions they are equivalent. Furthermore, we propose a unified notation for the two approaches, which might contribute to the integration of the two areas

Reasoning with Contexts in Description Logics

Harmelen, F.A.H. van [Promotor]Schlobach, K.S. [Copromotor

Consistency-by-Construction Techniques for Software Models and Model Transformations

A model is consistent with given specifications (specs) if and only if all the specifications are held on the model, i.e., all the specs are true (correct) for the model. Constructing consistent models (e.g., programs or artifacts) is vital during software development, especially in Model-Driven Engineering (MDE), where models are employed throughout the life cycle of software development phases (analysis, design, implementation, and testing). Models are usually written using domain-specific modeling languages (DSMLs) and specified to describe a domain problem or a system from different perspectives and at several levels of abstraction. If a model conforms to the definition of its DSML (denoted usually by a meta-model and integrity constraints), the model is consistent. Model transformations are an essential technology for manipulating models, including, e.g., refactoring and code generation in a (semi)automated way. They are often supposed to have a well-defined behavior in the sense that their resulting models are consistent with regard to a set of constraints. Inconsistent models may affect their applicability and thus the automation becomes untrustworthy and error-prone. The consistency of the models and model transformation results contribute to the quality of the overall modeled system. Although MDE has significantly progressed and become an accepted best practice in many application domains such as automotive and aerospace, there are still several significant challenges that have to be tackled to realize the MDE vision in the industry. Challenges such as handling and resolving inconsistent models (e.g., incomplete models), enabling and enforcing model consistency/correctness during the construction, fostering the trust in and use of model transformations (e.g., by ensuring the resulting models are consistent), developing efficient (automated, standardized and reliable) domain-specific modeling tools, and dealing with large models are continually making the need for more research evident. In this thesis, we contribute four automated interactive techniques for ensuring the consistency of models and model transformation results during the construction process. The first two contributions construct consistent models of a given DSML in an automated and interactive way. The construction can start at a seed model being potentially inconsistent. Since enhancing a set of transformations to satisfy a set of constraints is a tedious and error-prone task and requires high skills related to the theoretical foundation, we present the other contributions. They ensure model consistency by enhancing the behavior of model transformations through automatically constructing application conditions. The resulting application conditions control the applicability of the transformations to respect a set of constraints. Moreover, we provide several optimizing strategies. Specifically, we present the following: First, we present a model repair technique for repairing models in an automated and interactive way. Our approach guides the modeler to repair the whole model by resolving all the cardinalities violations and thereby yields a desired, consistent model. Second, we introduce a model generation technique to efficiently generate large, consistent, and diverse models. Both techniques are DSML-agnostic, i.e., they can deal with any meta-models. We present meta-techniques to instantiate both approaches to a given DSML; namely, we develop meta-tools to generate the corresponding DSML tools (model repair and generation) for a given meta-model automatically. We present the soundness of our techniques and evaluate and discuss their features such as scalability. Third, we develop a tool based on a correct-by-construction technique for translating OCL constraints into semantically equivalent graph constraints and integrating them as guaranteeing application conditions into a transformation rule in a fully automated way. A constraint-guaranteeing application condition ensures that a rule applies successfully to a model if and only if the resulting model after the rule application satisfies the constraint. Fourth, we propose an optimizing-by-construction technique for application conditions for transformation rules that need to be constraint-preserving. A constraint-preserving application condition ensures that a rule applies successfully to a consistent model (w.r.t. the constraint) if and only if the resulting model after the rule application still satisfies the constraint. We show the soundness of our techniques, develop them as ready-to-use tools, evaluate the efficiency (complexity and performance) of both works, and assess the overall approach in general as well. All our four techniques are compliant with the Eclipse Modeling Framework (EMF), which is the realization of the OMG standard specification in practice. Thus, the interoperability and the interchangeability of the techniques are ensured. Our techniques not only improve the quality of the modeled system but also increase software productivity by providing meta-tools for generating the DSML tool supports and automating the tasks

A journey back home through a mask for the 21st century : the legacy of Commedia dell'Arte in postdramatic theatre with particular focus on the centrality of the actor in devised performance : a practice-as-research PhD based on three years of research, culminating in this thesis, an ensemble devised performance A Floating Caravan Under the Moon (2015/16) and a solo piece Home/Finding Home (2017/18)

This study aims to cast new light on our understanding, interpretation and practical explorations of Commedia dell’Arte’s legacy and continuing relevance to contemporary performance. An original contribution to contemporary studies on the Commedia dell’Arte, this research highlights the striking similarities between Commedia’s core principles and Lehmann’s postdramatic theatre. Rather than a reinterpretation or re-contextualisation, my work can be described as a reinvention of Commedia Masks through a rediscovery of Commedia dell’Arte’s principles, as discussed by Flaminio Scala in his prologue to Il Finto Marito (1619); first and foremost, the notion of ‘Actor as Creator’ that is foundational to my practice. Utilising the ensemble devised piece, A Floating Caravan Under the Moon, and the solo-piece Home as case studies, this thesis discusses and analyses my work as a tutor, a director and a performer. It explores the efficacy of my physical approach to characterisation; more specifically my use of autobiographical material and Commedia dell’Arte techniques to develop a new Mask for the 21st century: the ‘Experiential Mask’. Moving beyond the traditional notion of Mask as fixed-type or stock character, this alive, malleable and adaptable Mask is created by the actors in response to their reality, their world and their culture. In answering the research question: How to develop a devising methodology drawing from Commedia dell’Arte’s techniques and principles without necessarily utilising the traditional types, masks and aesthetic? This thesis evaluates my approach to devising discussing three main areas of practice: my ethos (Chapter 3.1: Artisan Theatre), my dramaturgical approach (Chapter 3.2: Accidental Narratives) and my theatrical language (Chapter 3.3: Stage Resonances). Each chapter provides a contextualisation within postdramatic (devised) theatre, a description and evaluation of practical methodologies and an analysis of my findings. The Conclusions draw on my reflections, emphasising the similarities and differences with existing practices in the field and the originality of my work

Towards More Effective Tableaux Reasoning for CKR

Representation of context dependent knowledge in the Semantic Web is a recently emergent issue. A number of logical formalisms with this aim have been proposed [3, 11, 14]. Among them is the DL based Contextualized Knowledge Repository (CKR) [13]. One of the mostly advocated advantages of context based knowledge representation is tha

Railroads and Aspects of Social Change in Senegal, 1878-1933

In a dissertation, or any research subject for that matter, there are generally both narrow and broader queries that can be pursued on a given theme. The narrow theme in this case concerns the motives for French railroad-building in Senegal. Unfortunately, despite prolonged searches through archival sources available in Senegal, it soon became obvious that there were simply too many missing particulars to be able to complete this story well. Even while searching out the missing information gaps for the narrow theme, however, it also proved possible to gather abundant material for the broader theme of the social impact of the railroad in Senegal, on trade patterns, on labor, and on land— sufficient material at the end of a two-year sojourn in Senegal to write a dissertation regardless of the missing gaps in the narrow theme