Papers by Nikos Papadakis
EvoRDF: A Framework for Exploring Ontology Evolution
Lecture Notes in Computer Science
The evolution of ontologies is a reality in current research community. The problem of understand... more The evolution of ontologies is a reality in current research community. The problem of understanding and exploring this evolution is a fundamental problem as maintainers of depending artifacts need to take a decision about possible changes and ontology engineers need to understand the reasons for this evolution. Recent research focuses on identifying and statically visualizing deltas between ontology versions using various low- or high-level language of changes. In this paper, we argue that this is not enough and we provide a complete solution enabling the active, dynamic exploration of the evolution of RDF/S ontologies using provenance queries. To this direction, we construct an ontology of changes for modeling the language of changes and we store all changes as instances of this ontology in a triple store. On top of this triple store two visualization modules, one individual app and one protege plugin allow the exploration of the evolution using provenance queries. To the best of our knowledge our approach is unique in allowing the dynamic exploration of the evolution using provenance queries.
Real Time Evaluation of Education Methods via Smart Mobile Technology
We design, implement and evaluate performance of Exantas application which is compatible with And... more We design, implement and evaluate performance of Exantas application which is compatible with Android Operating Systems Smartphone devices. As Exantas tool was able to show ancients travelers the correct route to follow we show that our application can help educational staff to improve their skills and evaluate on the fly how efficient is the educational style that they follow. Results can help teachers measure while teaching how much of the lessons content has been successfully absorbed by students and what are the topics that need further analysis or even a completely new explanation approach. As experiments show, Exantas is able to reduce teaching efforts and to reveal real lessons comprehension status since Teachers can make multiple Questions to all students and receive answers in seconds. Moreover, all answers are processed anonymously ensuring anonymity and integrity since students are not afraid to provide their actual answer.
Knowledge graphs have now become common on the web, ranging from small taxonomies for categorizin... more Knowledge graphs have now become common on the web, ranging from small taxonomies for categorizing web sites, to large knowledge bases that contain a vast amount of structured content. To enable their quick understanding and exploration semantic summaries have been proposed. A key issue of structural semantic summaries is the identification of the most important nodes. Works in the area, usually employ a single centrality measure, capturing a specific perspective on the notion of a node’s importance. However, combining multiple centrality measures could give a more objective view, on which nodes should be selected as the most important ones. In this paper, we present SumMER, a novel framework that explores machine learning techniques for optimally combining multiple centrality measures for selecting the most important nodes. The experiments performed show the benefit of our approach, effectively increasing the quality of the generated summaries.
In this study, we developed an innovating Android application in order to display data from OWL o... more In this study, we developed an innovating Android application in order to display data from OWL ontologies. Using some tested technologies for Android development the application became stable and usable. Moreover, we created some new algorithms in order to decode, store and handle OWL ontologies at mobile devices. The first chapter is the introduction of our study. We summarize the structure of the project and we mention the general approach of our concept. Developing an ontology exploration application for mobile devices in order to not spending time when we loaded them to Protégé, like previous in Android application. We present the comparison results at the following table: Android app time
Reasoning about action and change has been one of the main research themes of the knowledge repre... more Reasoning about action and change has been one of the main research themes of the knowledge representation and planning communities of the last years Action theories providing an axiomatic basis for managing change are applicable to a wide area of disciplines including software engi neering cognitive robotics and data knowledge base systems In this paper we review action theories proposed for reasoning about the dynamics of database systems We examine how these theories deal with the three infamous problems associated with this area namely a the frame problem which refers to the identi cation of predicates or functions that remain unchanged as a result of action execution b the rami cation problem which refers to determining the indirect e ects of actions and c the quali cation problem which refers to determining the preconditions which must hold prior to the exe cution of an action We brie y describe the solutions which have been proposed for these problems and position these probl...
Ontologies are widely used nowadays. However, the plethora of ontologies currently available onli... more Ontologies are widely used nowadays. However, the plethora of ontologies currently available online, makes it really difficult to identify which ontologies are appropriate for a given task and to decide on their quality characteristics. This is further complicated by the fact that multiple quality criteria have been proposed for ontologies, making it even more difficult to decide which ontology to adopt. In this context, in this paper we present Delta, a modular online tool for analyzing and evaluating ontologies. The interested user can upload an ontology to the tool, which then automatically analyzes it and graphically visualizes numerous statistics, metrics, and pitfalls. Those visuals presented include a diverse set of quality dimensions, further guiding users to understand the benefits and the drawbacks of each individual ontology and how to properly develop and extend it.
As more and more data become available as linked data, the need for efficient and effective metho... more As more and more data become available as linked data, the need for efficient and effective methods for their exploration becomes apparent. Semantic summaries try to extract meaning from data, while reducing its size. State of the art structural semantic summaries, focus primarily on the graph structure of the data, trying to maximize the summary’s utility for query answering, i.e. the query coverage. In this poster paper, we present an algorithm, trying to maximize the aforementioned query coverage, using ideas borrowed from result diversification. The key idea of our algorithm is that, instead of focusing only to the “central” nodes, to push node selection also to the perimeter of the graph. Our experiments show the potential of our algorithm and demonstrate the considerable advantages gained for answering larger fragments of user queries.
AthPPA: A Data Visualization Tool for Identifying Political Popularity over Twitter
Information
Sentiment Analysis is an actively growing field with demand in both scientific and industrial sec... more Sentiment Analysis is an actively growing field with demand in both scientific and industrial sectors. Political sentiment analysis is used when a data analyst wants to determine the opinion of different users on social media platforms regarding a politician or a political event. This paper presents Athena Political Popularity Analysis (AthPPA), a tool for identifying political popularity over Twitter. AthPPA is able to collect in-real-time tweets and for each tweet to extract metadata such as number of likes, retweets per tweet etc. Then it processes their text in order to calculate their overall sentiment. For the calculation of sentiment analysis, we have implemented a sentiment analyzer that is able to identify the grammatical issues of a sentence as well as a lexicon of negative and positive words designed specifically for political sentiment analysis. An analytic engine processes the collected data and provides different visualizations that provide additional insights on the c...
Algorithms
Chatbots, also known as conversation agents, are programs that are able to simulate and reproduce... more Chatbots, also known as conversation agents, are programs that are able to simulate and reproduce an intelligent conversation with humans. Although this type of program is not new, the explosion of the available information and the rapid increase of the users seeking this information have renewed the interest in their development. In this paper, we present R2D2, an intelligent chatbot relying on semantic web technologies and offering an intelligent controlled natural language interface for accessing the information available in DBpedia. The chatbot accepts structured input, allowing users to enter triple-pattern like queries, which are answered by the underlying engine. While typing, an auto-complete service guides users on creating the triple patterns, suggesting resources available in the DBpedia. Based on user input (in the form of triple-pattern like queries), the corresponding SPARQL queries are automatically formulated. The queries are submitted to the corresponding DBpedia SP...
EvoRDF: evolving the exploration of ontology evolution
The Knowledge Engineering Review
Ontologies are constantly evolving as new requirements daily occur and the modeling choices of th... more Ontologies are constantly evolving as new requirements daily occur and the modeling choices of the past should be updated or adapted. Exploring this evolution will enhance the understanding, augmenting the exploitation potential of the available ontologies. However, recent research focuses mostly on detecting changes between ontology versions, overloading end-users with hundreds or even thousands of changes between ontology versions, making it impossible to explore this evolution. To this direction, in this paper, we present EvoRDF, a novel framework for exploring ontology evolution using provenance queries. Our approach uses a high-level language of changes and effectively answers queries about when a specific resource was introduced and how—by which change operations. Even more, why queries can identify the sequence of changes that led to the creation of a specific resource in the latest ontology version or track the evolution of a specific resource from a past ontology version. T...
EAI Endorsed Transactions on Creative Technologies
We design, implement and evaluate performance of Exantas application which is compatible with And... more We design, implement and evaluate performance of Exantas application which is compatible with Android Operating System Smartphone devices. As Exantas tool was able to show ancients travelers the correct route to follow, we show that our application can help educational staff to improve their skills and evaluate on the fly how efficient is the educational style that they follow. Results can help teachers measure while teaching how much of the lessons content has been successfully absorbed by students and what are the topics that need further analysis or even a completely new explanation approach. Moreover, teachers are now able to perform quickly and without effort, small evaluation tests during their lessons for each student individually and keep tracking of their overall semester performance, concluding in a more extensive, generic and reliable grading system. As experiments show, Exantas is able to reduce teaching efforts and to reveal real lessons comprehension status since teachers can make multiple Questions to all students and receive answers in seconds. Moreover, all queries are processed anonymously ensuring anonymity and integrity since students are not afraid to provide their actual answers when teaching method is evaluated, and individually for each account when students' performance is checked.
AmbISPDM
Applied Intelligence
A Solution to the Rami cation Problem Expressed in Temporal Description Logics
International Journal of Semantic Computing, 2014
International Journal of Knowledge-based and Intelligent Engineering Systems, 2014
This paper presents an interactive verifier for logic programs. These logic programs are construc... more This paper presents an interactive verifier for logic programs. These logic programs are constructed by a schema-based method. Each program is associated with proof schemes due to the program development method. The correctness proof of a program is guided by its associated proof schemes. The main components of the verifier are the prover which carries out the proof steps, the knowledge base (KB) which includes representations of all theories and transformation rules, the KB update which supports the update of KB and the graphical user interface (GUI). The emphasis in the design of this proof checker is on effective guidance of the proof based on the activated proof schemes and on performance by the verifier of tedious, trivial and time consuming tasks. The difficult proof decisions are taken by the user, then, the proof checker applies them. The design of the interface is based on providing the user the required support for the proof of a theorem and for the update of KB. This system is an effective and useful tool for the interactive verification of non-trivial logic programs.
International Journal of Knowledge-based and Intelligent Engineering Systems, 2012
The correctness of logic programs which are constructed by a schema-based method is presented in ... more The correctness of logic programs which are constructed by a schema-based method is presented in this paper. This schema-based method constructs typed, moded logic programs by stepwise top-down design using five program schemata, data types and modes. Correctness proofs in this approach are guided by the constructed logic programs. A proof scheme is proposed for each program schema. It is claimed that the structure of a logic program constructed by this schema-based method is reflected in the structure of its correctness proof. The proof schemes which correspond to design schemata are followed in the correctness proofs of logic programs.
This paper presents the design of an interactive verifier or proof checker for logic programs. Th... more This paper presents the design of an interactive verifier or proof checker for logic programs. These logic programs are constructed by a schema-based method. This design is divided in the design of the proof checker, the design of the interface and the representation of the knowledge base. The emphasis in the design of the interface is on the provision of the required assistance to the user for the proof of a theorem. In addition, it provides support for the update of the knowledge base. Special importance in the design is on the performance by the verifier of tedious, trivial and time consuming tasks. The difficult proof decisions are taken by the user, then, our proof checker applies these proof decisions. The main design criterion for the knowledge representation is the support for an efficient and modular implementation of the verifier.
Logic in computer science describes topics where reasoning models are applied to the representati... more Logic in computer science describes topics where reasoning models are applied to the representation of knowledge and artificial intelligence. The use of distributed systems in solving logic problems is an intriguing but also challenging topic and algorithms of pruning network queries result in optimization of the resolution process. The current study suggests an implemented tool of a Distributed Peer-To-Peer Reasoning model, where local reasoning rules with incomplete facts are evaluated. This is achieved by sending queries of the neededfacts to peers, using a protocol that relieves the network from unnecessary queries and queries that linger and circle around
Access to Relational Databases with english language
A Tool for Spatial Reasoning in XML Documents
International Journal of Semantic Computing, 2015
In this paper, we study the ramification problem in the setting of spatial xml data. Standard sol... more In this paper, we study the ramification problem in the setting of spatial xml data. Standard solutions from the literature on reasoning about action are inadequate because they cannot capture integrity constraints in spatial data. In this paper, we provide a solution to the ramification problem based on situation calculus. We present a tool that connects the theoretical results with the practical considerations, by producing the User Interface in C# in order to address the ramification problem in spatial XML file in specific time period. a
This master thesis considers the problem of routing flows belonging to different Classes of Servi... more This master thesis considers the problem of routing flows belonging to different Classes of Services with different QoS requirements across MPLS capable networks. At first the functional capabilities are specified that need to be supported in order to optimize network resource utilization, and satisfy business - or service - or network-level QoS requirements in a scalable and controlled manner. The thesis focuses on the design of an architecture appropriate to combine MPLS with QoS-Policy based routing capable components. Existing label switching technologies assume that routing is accomplished basically using traditional network layer routing protocols. Consequently network administrators have no control on the way traffic navigates within the network. This can easily lead to undesirable situations where some parts of the network are congested and some others are underutilized. Future Internet imposes the demand for advanced network control and management mechanisms. Combining labe...
Uploads
Papers by Nikos Papadakis