Governments and public administrations started recently to publish large amounts of structured da... more Governments and public administrations started recently to publish large amounts of structured data on the Web, mostly in the form of tabular data such as CSV files or Excel sheets. Various tools and projects have been launched aiming at facilitating the lifting of tabular data to reach semantically structured and linked data. However, none of these tools supported a truly incremental, pay-as-you-go data publication and mapping strategy, which enables effort sharing between data owners, community experts and consumers. In this article, we present an approach for enabling the user-driven semantic mapping of large amounts tabular data. We devise a simple mapping language for tabular data, which is easy to understand even for casual users, but expressive enough to cover the vast majority of potential tabular mappings use cases. We outline a formal approach for mapping tabular data to RDF. Default mappings are automatically created and can be revised by the community using a semantic wiki. The mappings are executed using a sophisticated streaming RDB2RDF conversion. We report about the deployment of our approach at the Pan-European data portal PublicData.eu, where we transformed and enriched almost 10,000 datasets accounting for 7.3 billion triples.
The constantly growing amount of Linked Open Data (LOD) datasets constitutes the need for rich me... more The constantly growing amount of Linked Open Data (LOD) datasets constitutes the need for rich metadata descriptions, enabling users to discover, understand and process the available data. This metadata is often created, maintained and stored in diverse data repositories featuring disparate data models that are often unable to provide the metadata necessary to automatically process the datasets described. This paper proposes DataID, a best-practice for LOD dataset descriptions which utilize RDF files hosted together with the datasets, under the same domain. We are describing the data model, which is based on the widely used DCAT and VoID vocabularies, as well as supporting tools to create and publish DataIDs and use cases that show the benefits of providing semantically rich metadata for complex datasets. As a proof of concept, we generated a DataID for the DBpedia dataset, which we will present in the paper.
This demo presents LODStats, a web application for collection and exploration of the Linked Open ... more This demo presents LODStats, a web application for collection and exploration of the Linked Open Data statistics. LODStats consists of two parts: the core collects statistics about the LOD cloud and publishes it on the LODStats web portal, a front-end for exploration of dataset statistics. Statistics are published both in human-readable and machine-readable formats, thus allowing consumption of the data through web front-end by the users as well as through an API by services and applications. As an example for the latter we showcase how to visualize the statistical data with the CubeViz application.
The Web of Data has grown enormously over the last years. Currently, it comprises a large compend... more The Web of Data has grown enormously over the last years. Currently, it comprises a large compendium of interlinked and distributed datasets from multiple domains. Running complex queries on this compendium often requires accessing data from different endpoints within one query. The abundance of datasets and the need for running complex query has thus motivated a considerable body of work on SPARQL query federation systems, the dedicated means to access data distributed over the Web of Data. However, the granularity of previous evaluations of such systems has not allowed deriving of insights concerning their behaviour in different steps involved during federated query processing. In this work, we perform extensive experiments to compare state-of-the-art SPARQL endpoint federation systems using the comprehensive performance evaluation framework FedBench. In addition to considering the tradition query runtime as an evaluation criterion, we extend the scope of our performance evaluation by considering criteria, which have not been paid much attention to in previous studies. In particular, we consider the number of sources selected, the total number of SPARQL ASK requests used, the completeness of answers as well as the source selection time. Yet, we show that they have a significant impact on the overall query runtime of existing systems. Moreover, we extend FedBench to mirror a highly distributed data environment and assess the behaviour of existing systems by using the same performance criteria. As the result we provide a detailed analysis of the experimental outcomes that reveal novel insights for improving current and future SPARQL federation systems.
Abstract. Up to the present day much effort has been made to publish government data on the Web. ... more Abstract. Up to the present day much effort has been made to publish government data on the Web. However, such data has been published in different formats. For any particular source and use (eg exploration, visualization, integration) of such information specific applications have to be written. This limits the overall usability of the information provided and makes it difficult to access information resources. These limitations can be overridden, if the information will be provided using a homogeneous data and access model complying ...
Knowledge Engineering and Knowledge Management, 2012
Presentations play a crucial role in knowledge management within organizations, in particular to ... more Presentations play a crucial role in knowledge management within organizations, in particular to facilitate organizational learning and innovation. Much of the corporate strategy, direction and accumulated knowledge within organizations is encapsulated in presentations. In this paper, we investigate the limitations of current presentation tools for semi-structured knowledge representation and sharing within organizations. We address challenges such as collaborative creation of presentations, tracking changes within them, ...
Recently, a large number of open data repositories, catalogs and portals have been emerging in th... more Recently, a large number of open data repositories, catalogs and portals have been emerging in the scientific and government realms. In this chapter, we characterise this newly emerging class of information systems. We describe the key functionality of open data portals, present a conceptual model and showcase the pan-European data portal PublicData.eu as a prominent example. Using examples from Serbia and Poland, we present an approach for lifting the often semantically shallow datasets registered at such data portals to Linked Data in order to make data portals the backbone of a distributed global data warehouse for our information society on the Web.
It is the core business of the information industry, including traditional publishers and media a... more It is the core business of the information industry, including traditional publishers and media agencies, to deal with content, data and information. Therefore, the development and adaptation of Linked Data and Linked Open Data technologies to this industry is a perfect fit. As a concrete example, the processing of legal information at Wolters Kluwer as a global legal publisher through the whole data life cycle is introduced. Further requirements, especially in the field of governance, maintenance and licensing of data are developed in detail. The partial implementation of this technology in the operational systems of Wolters Kluwer shows the relevance and usefulness of this technology.
Governments and public administrations started recently to publish large amounts of structured da... more Governments and public administrations started recently to publish large amounts of structured data on the Web, mostly in the form of tabular data such as CSV files or Excel sheets. Various tools and projects have been launched aiming at facilitating the lifting of tabular data to reach semantically structured and linked data. However, none of these tools supported a truly incremental, pay-as-you-go data publication and mapping strategy, which enables effort sharing between data owners, community experts and consumers. In this article, we present an approach for enabling the user-driven semantic mapping of large amounts tabular data. We devise a simple mapping language for tabular data, which is easy to understand even for casual users, but expressive enough to cover the vast majority of potential tabular mappings use cases. We outline a formal approach for mapping tabular data to RDF. Default mappings are automatically created and can be revised by the community using a semantic wiki. The mappings are executed using a sophisticated streaming RDB2RDF conversion. We report about the deployment of our approach at the Pan-European data portal PublicData.eu, where we transformed and enriched almost 10,000 datasets accounting for 7.3 billion triples.
The constantly growing amount of Linked Open Data (LOD) datasets constitutes the need for rich me... more The constantly growing amount of Linked Open Data (LOD) datasets constitutes the need for rich metadata descriptions, enabling users to discover, understand and process the available data. This metadata is often created, maintained and stored in diverse data repositories featuring disparate data models that are often unable to provide the metadata necessary to automatically process the datasets described. This paper proposes DataID, a best-practice for LOD dataset descriptions which utilize RDF files hosted together with the datasets, under the same domain. We are describing the data model, which is based on the widely used DCAT and VoID vocabularies, as well as supporting tools to create and publish DataIDs and use cases that show the benefits of providing semantically rich metadata for complex datasets. As a proof of concept, we generated a DataID for the DBpedia dataset, which we will present in the paper.
This demo presents LODStats, a web application for collection and exploration of the Linked Open ... more This demo presents LODStats, a web application for collection and exploration of the Linked Open Data statistics. LODStats consists of two parts: the core collects statistics about the LOD cloud and publishes it on the LODStats web portal, a front-end for exploration of dataset statistics. Statistics are published both in human-readable and machine-readable formats, thus allowing consumption of the data through web front-end by the users as well as through an API by services and applications. As an example for the latter we showcase how to visualize the statistical data with the CubeViz application.
The Web of Data has grown enormously over the last years. Currently, it comprises a large compend... more The Web of Data has grown enormously over the last years. Currently, it comprises a large compendium of interlinked and distributed datasets from multiple domains. Running complex queries on this compendium often requires accessing data from different endpoints within one query. The abundance of datasets and the need for running complex query has thus motivated a considerable body of work on SPARQL query federation systems, the dedicated means to access data distributed over the Web of Data. However, the granularity of previous evaluations of such systems has not allowed deriving of insights concerning their behaviour in different steps involved during federated query processing. In this work, we perform extensive experiments to compare state-of-the-art SPARQL endpoint federation systems using the comprehensive performance evaluation framework FedBench. In addition to considering the tradition query runtime as an evaluation criterion, we extend the scope of our performance evaluation by considering criteria, which have not been paid much attention to in previous studies. In particular, we consider the number of sources selected, the total number of SPARQL ASK requests used, the completeness of answers as well as the source selection time. Yet, we show that they have a significant impact on the overall query runtime of existing systems. Moreover, we extend FedBench to mirror a highly distributed data environment and assess the behaviour of existing systems by using the same performance criteria. As the result we provide a detailed analysis of the experimental outcomes that reveal novel insights for improving current and future SPARQL federation systems.
Abstract. Up to the present day much effort has been made to publish government data on the Web. ... more Abstract. Up to the present day much effort has been made to publish government data on the Web. However, such data has been published in different formats. For any particular source and use (eg exploration, visualization, integration) of such information specific applications have to be written. This limits the overall usability of the information provided and makes it difficult to access information resources. These limitations can be overridden, if the information will be provided using a homogeneous data and access model complying ...
Knowledge Engineering and Knowledge Management, 2012
Presentations play a crucial role in knowledge management within organizations, in particular to ... more Presentations play a crucial role in knowledge management within organizations, in particular to facilitate organizational learning and innovation. Much of the corporate strategy, direction and accumulated knowledge within organizations is encapsulated in presentations. In this paper, we investigate the limitations of current presentation tools for semi-structured knowledge representation and sharing within organizations. We address challenges such as collaborative creation of presentations, tracking changes within them, ...
Recently, a large number of open data repositories, catalogs and portals have been emerging in th... more Recently, a large number of open data repositories, catalogs and portals have been emerging in the scientific and government realms. In this chapter, we characterise this newly emerging class of information systems. We describe the key functionality of open data portals, present a conceptual model and showcase the pan-European data portal PublicData.eu as a prominent example. Using examples from Serbia and Poland, we present an approach for lifting the often semantically shallow datasets registered at such data portals to Linked Data in order to make data portals the backbone of a distributed global data warehouse for our information society on the Web.
It is the core business of the information industry, including traditional publishers and media a... more It is the core business of the information industry, including traditional publishers and media agencies, to deal with content, data and information. Therefore, the development and adaptation of Linked Data and Linked Open Data technologies to this industry is a perfect fit. As a concrete example, the processing of legal information at Wolters Kluwer as a global legal publisher through the whole data life cycle is introduced. Further requirements, especially in the field of governance, maintenance and licensing of data are developed in detail. The partial implementation of this technology in the operational systems of Wolters Kluwer shows the relevance and usefulness of this technology.
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Papers by Ivan Ermilov