Matias Frosterus

ONKI SKOS Server for Publishing and Utilizing SKOS Vocabularies and Ontologies as Services

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.

CultureSampo: A National Publication System of Cultural Heritage on the Semantic Web 2.0

CultureSampo is an application demonstration of a national level publication system of cultural heritage contents on the Web, based on ideas and technologies of the Semantic (Web and) Web 2.0. On the semantic side, the system presents new solutions to interoperability problems of dealing with multiple ontologies of different domains, and to problems of integrating multiple metadata schemas and cross-domain content into a homogeneous semantic portal. A novelty of the system is to use semantic models based on events and narrative process descriptions for modeling and visualizing cultural phenomena, and for semantic recommendations. On the Web 2.0 side, CultureSampo proposes and demonstrates a content creation process for collaborative, distributed ontology and content development including different memory organizations and citizens. The system provides the cultural heritage contents to end-users in a new way through multiple (nine) thematic perspectives, based on semantic visualizations. Furthermore, CultureSampo services are available for external web-applications to use through semantic AJAX widgets.

Elements of a National SemanticWeb Infrastructure--Case Study Finland on the Semantic Web

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.

Data finland: a semantic portal for open and linked datasets

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 Finnish Law as a Linked Data Service

Juridical information is important to organizations and individuals alike and is linked to from all walks of life. The Finnish government has published the Finlex Data Bank for searching and browsing legislation documents. However, the data there is not yet open, is based on a traditional XML schema, and does not conform to new semantic metadata standards. There are many difficulties in maintaining and using the site in, e.g., data harvesting, interoperability, querying, and linking that could be mitigated by the Semantic Web technologies. This paper presents an approach and a project—including first results—for publishing and using the Finnish legislation as a 5-star Linked Open Data service.

Creating and Publishing Semantic Metadata about Linked and Open Datasets

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 various formats, not only in RDF. However, the metadata available for these datasets is often minimal, heterogeneous, and distributed, which makes finding a suitable dataset for a given need problematic. Governmental open datasets are often the basis of innovative applications but the datasets need to be found by the developers first. To address the problem, we present a distributed content creation model and tools for annotating and publishing metadata about linked data and non-RDF datasets on the web. The system DATAFINLAND is based on a modified version of the VoiD vocabulary for describing linked RDF datasets, and uses an online metadata editor SAHA3 connected to ONKI ontology services for annotating contents semantically. The resulting metadata can be published instantly on an integrated faceted search and browsing engine HAKO for human users, as a SPARQL end-point for machine use, and as a source file. As a proof of concept, the system has been applied to LOD and Finnish governmental datasets.

Linked Open Ontology Cloud KOKO—Managing a System of Cross-Domain Lightweight Ontologies

The Linked Data movement has focused on building cross-domain interoperability by creating and using (typically) owl:sameAs mappings between the datasets in the Linked Data Cloud (LOD). However, when linking data, ontologies would allow for deeper interoperability. Because different ontologies have been used when annotating different datasets, we argue that the LOD cloud needs to be complemented by developing a lightweight “Linked Open Ontology Cloud” (LOO). Aligning the ontologies requires more refined techniques than mapping data instances for the LOD.

Semantic Entity Search Diversification

We present an approach to diversify entity search by utilizing semantics present and inferred from the initial entity search results. Our approach makes use of ontologies and independent component analysis of the entity descriptions to reveal direct and latent semantic connections between the entities present in the initial search results. The semantic connections are then used to sample a set of diverse entities. We empirically demonstrate the performance of our approach through retrieval experiments that use a real-world dataset composed from four entity databases. The results indicate that our approach significantly improves both diversity and effectiveness of entity search.

Linked Open Ontology cloud: managing a system of interlinked cross-domain lightweight ontologies

Traditionally, the structure of the controlled vocabularies used for annotation can be utilised for reasoning for information retrieval. However, this can be problematic when applied in the Linked Data context. Linked Data typically comes from different organisations and domains with mutually incompatible vocabularies without explicit links between them resulting in data silos. This paper argues that to solve the problem one has to transform the annotation vocabularies into a Linked Open Ontology cloud. We present a method for transforming a set of legacy thesauri into a cloud of interlinked ontologies while ensuring the validity of the transitive subclass relations and the means for maintaining the system when component ontologies are updated. Our approach has been used and evaluated in practice building a cloud called KOKO of 16 ontologies, with a total of 47,000 concepts. KOKO has been published as an ontology service and is in use in various organisations for both data indexing and semantic search.