Matias Frosterus

Manufacturing companies face the challenge of maintaining documentation and knowledge about their projects and products, scattered in heterogenous, distributed databases, represented in different formats and languages, and hosted in mutually incompatible systems. At the same time, the knowledge needs to be accessed on a global level from different perspectives and user groups, such as project planners, designers, and maintenance personnel. This paper presents a case study, based on real datasets of a major international diesel engine and power plant manufacturer, where these problems are addressed simultaneuosly by harmonizing the datasets from different sources using RDF, and by linking them together into a global repository using shared resources. Based on the global RDF store, services for both human and machine users, such as a faceted search engine and a SPARQL end-point, can be provided to support access from different perspectives to the company knowledge base.

We present a comprehensive system for producing interoperable metadata for Linked Open datasets and governmental datasets published in various formats.

Semantic web technologies have introduced the idea of annotating content in terms of concepts taken from ontologies. Since concepts are defined in terms of properties and relations to other concepts, descriptions grow up into larger RDF graphs that can be used as a basis for data integration and intelligent information retrieval. Since ontologies do not typically contain all the possible concepts needed for annotation, it is usually necessary to offer the annotator the possibility to introduce new free keywords or tags in addition to the predefined ontology concepts. The problem then is that free keywords/tags do not have ontological connections to the rest of the RDF graph, unless such relations are defined by the annotator.We present a process for integrating free keywords into the ontological framework, and a practical tool implementation of it, discussing the challenges and possibilities introduced by the system. We also describe a case study performed for the Finnish Defence Forces, where the tool is used for creating a faceted semantic search portal featuring the free keywords and the ontological concepts at the same time.

We consider ontology evolution in a system of light-weight Linked Data ontologies, aligned with each other to form a larger ontology system. When one ontology changes, the human editor must keep track of the actual changes and of the modifications needed in the related ontologies in order to keep the system consistent. This paper presents an analysis tool MUTU, by which such changes and their potential effects on other ontologies can be found. Such an analysis is useful for the ontology editors for understanding the differences between ontology versions, and for updating linked ontologies when changes occurred in other components of an ontology system.

The number of open datasets available on the web is increasing rapidly with the rise of the Linked Open Data (LOD) cloud and various governmental efforts for releasing public data in different formats, not only in RDF. The aim in releasing open datasets is for developers to use them in innovative applications, but the datasets need to be found first and metadata available is often minimal, heterogeneous, and distributed making the search for the right dataset often problematic. To address the problem, we present DataFinland, a semantic portal featuring a distributed content creation model and tools for annotating and publishing metadata about LOD and non-RDF datasets on the web. The metadata schema for DataFinland is based on a modified version of the voiD vocabulary for describing linked RDF datasets, and annotations are done using an online metadata editor SAHA connected to ONKI ontology services providing a controlled set of annotation concepts. The content is published instantly on an integrated faceted search and browsing engine HAKO for human users, and as a SPARQL endpoint and a source file for machines. As a proof of concept, the system has been applied to LOD and Finnish governmental datasets.

The Semantic Web extends traditional web documents, i.e. the Web of Pages, with conceptual structures based on ontologies and metadata, i.e. the Web of Data. This paper presents a hybrid document search approach combining the benefits of the traditional text search of literal documents and the semantic search based on their underlying conceptual structures. The approach is based on document expansion, where documents are automatically annotated with not only the concepts explicitly present in a given document, but also with the ontologically related concepts using smaller weights. Our test results using the CLEF Test Suite suggest that document expansion alone achieves better recall than text search at the expense of precision. As a solution, a method of combining document expansion with text search is presented in which better recall was obtained without sacrificing precision. This approach seems promising when integrating unstructured, textual content with the Semantic Web of Data.

Vocabularies are the building blocks of the Semantic Web providing shared terminological resources for content indexing, information retrieval, data exchange, and content integration. Most semantic web applications in practical use are based on lightweight ontologies and, more recently, on the Simple Knowledge Organization System (SKOS) data model being standardized by W3C. Easy and cost-efficient publication, integration, and utilization methods of vocabulary services are therefore highly important for the proliferation of the Semantic Web. This paper presents the ONKI SKOS Server for these tasks. Using ONKI SKOS, a SKOS vocabulary or a lightweight ontology can be published on the web as ready-to-use services in a matter of minutes. The services include not only a browser for human usage, but also Web Service and AJAX interfaces for concept finding, selecting and transporting resources from the ONKI SKOS Server to connected systems. Code generation services for AJAX and Web Service APIs are provided automatically, too. ONKI SKOS services are also used for semantic query expansion in information retrieval tasks. The idea of publishing ontologies as services is analogous to Google Maps. In our case, however, vocabulary services are provided and mashed-up in applications. ONKI SKOS was published in the beginning of 2008 and is to our knowledge the first generic SKOS server of its kind. The system has been used to publish and utilize some 60 vocabularies and ontologies in the National Finnish Ontology Service ONKI www.yso.fi.

This paper presents the national level cross-domain ontology and ontology service infrastructure ONKI used in Finland. The novelty of ONKI is based on two ideas. First, the core ontologies are developed collaboratively by experts transforming thesauri into mutually aligned lightweight ontologies, based on a large top ontology that is extended by various domain specific ontologies. Second, the National Ontology Service ONKI has been implemented for publishing ontologies cost-efficiently as ready to use services. ONKI provides legacy and other applications with ready to use functionalities for using ontologies on the HTML level by Ajax and semantic widgets. ONKI has been used in various applications for creating mash-up applications in a way analogous to using Google Maps, but in our case external applications are mashed-up with ontology support for indexing and information retrieval.

Thesauri and other controlled vocabularies act as building blocks of the Semantic Web by providing shared terminology for facilitating information retrieval, data exchange and integration. Representation and publishing methods are needed for utilizing thesauri efficiently, e.g., in content indexing and searching. W3C has provided the Simple Knowledge Organization System (SKOS) data model for expressing concept schemes, such as thesauri. A standard representation format for thesauri eliminates the need for implementing thesaurus specific rules or applications for processing them. However, there do not exist general tools which provide out of the box support for publishing and utilizing SKOS vocabularies in applications, without needing to implement application specific user interfaces for end users. For solving this problem the ONKI-SKOS server is presented.

Informaation lisääntyessä yhteiskunnassa vaaditaan sen tehokasta käsittelyä yhä enemmän ammattilaisten lisäksi myös tavallisilta käyttäjiltä. Tällöin luonnollinen pyrkimys on yksinkertaistaa ja automatisoida tiedonhakuprosessia mahdollisimman paljon, johon semanttisen webin tekniikat tarjoavat uusia mahdollisuuksia. Tässä diplomityössä tutkittiin mahdollisuuksia dokumentin laajentamisen ja ontologisten käsitteiden hyödyntämisen kautta parantaa tiedonhakuprosessia tekstipohjaiseen aineistoon, kuten sanomalehtiarkistoon. Tätä tarkoitusta varten luotiin automaattinen annotointi ja hakusovellus Airo, joka suorittaa jonkin annetun ontologian pohjalta dokumentin laajennuksen. Tämä tapahtuu ontologisella käsiteklusteroinnilla, jossa jonkin käsitteen esiintyminen tekstissä nostaa myös ontologian hierarkiassa läheisten käsitteiden painoa kyseistä dokumenttia indeksoitaessa ja haettaessa. Järjestelmän testit osoittivat, että käsitehaku yhdistettynä sanahakuun laskee haun tarkkuutta, mutta nostaa saantia. Sen sijaan hybridimenetelmä dokumentin- ja kyselyn laajennuksesta, jossa perinteisen sanahaun tuottamien dokumenttien käsitteillä suoritetaan laajentava haku, nosti saantia tarkkuuden kärsimättä. Luotu järjestelmä on ontologiariippumaton ja jokaisen ontologian tuottamat käsitteistykset talletetaan omaan indeksiinsä, jolloin niitä voidaan hakea erikseen.

This article presents the vision and results of creating the basis for a national semantic web content infrastructure in Finland in 2003-2007. The main elements of the infrastructure are shared and open metadata schemas, core ontologies, and public ontology services. Several practical applications testing and demonstrating the usefulness of the infrastructure are overviewed in the fields of eCulture, eHealth, eGovernment, eLearning, and eCommerce.