Yannis Marketakis

Modeling and querying provenance by extending CIDOC CRM

This paper elaborates on the problem of modeling provenance for both physical and digital objects. In particular it discusses provenance according to OAIS (ISO 14721:2003) and how it relates with the conceptualization of CIDOC CRM ontology (ISO 21127:2006). Subsequently it introduces an extension of the CIDOC CRM ontology, able to capture the modeling and the query requirements regarding the provenance of digital objects. Over this extension the paper provides a number of indicative examples of modeling provenance in various domains. Subsequently, it introduces a number of indicative provenance query templates, and finally it describes an implementation using Semantic Web technologies.

Integrating Heterogeneous and Distributed Information about Marine Species through a Top Level Ontology

One of the main characteristics of biodiversity data is its cross-disciplinary feature and the extremely broad range of data types, structures, and semantic concepts which encompasses. Moreover, biodiversity data, especially in the marine domain, is widely distributed, with few well-established repositories or standard protocols for their archiving, access, and retrieval. Our research aims at providing models and methods that allow integrating such information either for publishing it, browsing it, or querying it. For providing a valid and reliable knowledge ground for enabling semantic interoperability of marine data, in this paper we motivate a top level ontology, called MarineTLO that we have designed for this purpose, and discuss its use for creating MarineTLO-based warehouses in the context of a research infrastructure.

Mitos: Design and Evaluation of a DBMS-Based Web Search Engine

Engineering a Web search engine offering effective and efficient information retrieval is a challenging task. Mitos is a recently developed search engine that offers a wide spectrum of functionalities. A rather unusual design choice is that its index is based on an object-relational database system, instead of the classical inverted file. This paper discusses the benefits and the drawbacks of this choice (compared to inverted files), proposes three different database representations, and reports comparative experimental results. Two of these representations are one order of magnitude more space economical and two orders of magnitude faster in query evaluation, than the plain relational representation.

X3ML mapping framework for information integration in cultural heritage and beyond

The aggregation of heterogeneous data from different institutions in cultural heritage and e-science has the potential to create rich data resources useful for a range of different purposes, from research to education and public interests. In this paper, we present the X3ML framework, a framework for information integration that handles effectively and efficiently the steps involved in schema mapping, uniform resource identifier (URI) definition and generation, data transformation, provision and aggregation. The framework is based on the X3ML mapping definition language for describing both schema mappings and URI generation policies and has a lot of advantages when compared with other relevant frameworks. We describe the architecture of the framework as well as details on the various available components. Usability aspects are discussed and performance metrics are demonstrated. The high impact of our work is verified via the increasing number of international projects that adopt and use this framework.

Quantifying the Connectivity of a Semantic Warehouse and Understanding its Evolution over Time

In many applications one has to fetch and assemble pieces of information coming from more than one source for building a semantic warehouse offering more advanced query capabilities. In this paper the authors describe the corresponding requirements and challenges, and they focus on the aspects of quality and value of the warehouse. For this reason they introduce various metrics (or measures) for quantifying its connectivity, and consequently its ability to answer complex queries. The authors demonstrate the behaviour of these metrics in the context of a real and operational semantic warehouse, as well as on synthetically produced warehouses. The proposed metrics allow someone to get an overview of the contribution (to the warehouse) of each source and to quantify the value of the entire warehouse. Consequently, these metrics can be used for advancing data/endpoint profiling and for this reason the authors use an extension of VoID (for making them publishable). Such descriptions can be exploited for dataset/endpoint selection in the context of federated search. In addition, the authors show how the metrics can be used for monitoring a semantic warehouse after each reconstruction reducing thereby the cost of quality checking, as well as for understanding its evolution over time.

MatWare: Constructing and Exploiting Domain Specific Warehouses by Aggregating Semantic Data

In many applications one has to fetch and assemble pieces of information coming from more than one web sources such as SPARQL endpoints. In this paper we describe the corresponding requirements and challenges, based on our experience, and then we present a process and a tool that we have developed, called MatWare , for constructing such semantic warehouses. We focus on domain-specific warehouses, where the focus is given on the aspects of scope control, connectivity assessment, provenance, and freshness. MatWare (Materialized Warehouse) is a tool that automates the construction (and reconstruction) of such warehouses, and offers methods for tackling the aforementioned requirements. Finally we report our experiences from using it for building, maintaining and evolving an operational semantic warehouse for the marine domain, that is currently in use by several applications ranging from e-infrastructure services to smart phone applications.

Unifying heterogeneous and distributed information about marine species through the top level ontology MarineTLO

– Marine species data are scattered across a series of heterogeneous repositories and information systems. There is no repository that can claim to have all marine species data. Moreover, information on marine species are made available through different formats and protocols. The purpose of this paper is to provide models and methods that allow integrating such information either for publishing it, browsing it or querying it. Aiming at providing a valid and reliable knowledge ground for enabling semantic interoperability of marine species data, in this paper the authors motivate a top level ontology, called MarineTLO and discuss its use for creating MarineTLO-based warehouses. , – In this paper the authors introduce a set of motivating scenarios that highlight the need of having a top level ontology. Afterwards the authors describe the main data sources (Fisheries Linked Open Data, ECOSCOPE, WoRMS, FishBase and DBpedia) that will be used as a basis for constructing the MarineTLO. , – The paper discusses about the exploitation of MarineTLO for the construction of a warehouse. Furthermore a series of uses of the MarineTLO-based warehouse is being reported. , – In this paper the authors described the design of a top level ontology for the marine domain able to satisfy the need for maintaining integrated sets of facts about marine species and thus assisting ongoing research on biodiversity. Apart from the ontology the authors also elaborated with the mappings that are required for building integrated warehouses.

Assisting digital interoperability and preservation through advanced dependency reasoning

Digital material has to be preserved not only against loss or corruption, but also against changes in its ecosystem. A quite general view of the digital preservation problem is to approach it from a dependency management point of view. In this paper, we present a rule-based approach for dependency management which can model also converters and emulators. We show that this modeling approach enables the automatic reasoning needed for reducing the human effort required for checking (and monitoring) whether a task on a digital object is performable. We provide examples demonstrating how real-world converters and emulators can be modeled, and show how the preservation services can be implemented. Subsequently, we detail an implementation based on semantic web technologies, describe the prototype system Epimenides which demonstrates the feasibility of the approach, and finally report various promising evaluation results.

A Reference Architecture forVirtual Research Environments

This paper describes the Reference Architecture of the enhanced VRE (e-VRE), a Virtual Research Environment defined in the context of the VRE4EIC Project, funded by EU H2020 e-Infrastructure program. e-VRE is designed to overcome limits of existing VREs with respect to a number of orthogonal dimensions: improving the quality of VRE user experience by providing user centered, secure, privacy compliant, sustainable environments for accessing data, composing workflows and tracking data publications; increasing VRE usage in multidisciplinary research domains by abstracting and reusing building blocks and workflows from existing VRE initiatives; improving the interoperability of heterogeneous discovery, contextual and detailed metadata across all layers of the VRE.

LifeWatch Greece data-services: Discovering Biodiversity Data using Semantic Web Technologies

Abstract Background Biodiversity data is characterized by its cross-disciplinary character, the extremely broad range of data types and structures, and the variety of semantic concepts that it encompasses. Furthermore there is a plethora of different data sources providing resources for the same piece of information in a heterogeneous way. Even if we restrict our attention to Greek biodiversity domain, it is easy to see that biodiversity data remains unconnected and widely distributed among different sources. New information To cope with these issues, in the context of the LifeWatch Greece project, i) we supported cataloguing and publishing of all the relevant metadata information of the Greek biodiversity domain, ii) we integrated data from heterogeneous sources by supporting the definitions of appropriate models, iii) we provided means for efficiently discovering biodiversity data of interest and iv) we enabled the answering of complex queries that could not be answered from the individual sources. This work has been exploited, evaluated and scientificaly confirmed by the biodiversity community through the services provided by the LifeWatch Greece portal.