In our demonstration (with supportive poster) we want to present the Semantic Wiki application OntoWiki, which is an extensible tool for managing structured information in a collaborative, web-based environment. OntoWiki provides sophisticated means for navigating, visualising and authoring of RDF-based Knowledge Bases. It serves and consumes Linked Data and comprises a comprehensive middleware API for building custom Semantic Web applications. We refer to it as a Wiki, since our focus is on simplicity, adaptability and collaboration. However, other than annotating text-based Wiki pages with a special syntax (as suggested by text-based Semantic Wiki approaches), OntoWiki uses RDF in the rst place to represent information. For human users, OntoWiki allows to create di erent views on data, such as tabular representations or maps. For machine consumption it supports various RDF serialisations as well as RDFa, Linked Data and SPARQL interfaces. Since its introduction [1], the application has evolved into a framework for building Semantic Web applications [2] and was recently updated to support the collaboration across multiple domains and application via Semantic Pingback [3] and RDFauthor [5].
OntoWiki can be used to author, manage and publish RDF-based knowledge bases. In particular, our demonstration will focus on the following topics1. We have highlighted several phrases and keywords to give the reader a better overview on the main demonstration points.
OntoWiki provides a number of ways for navigating through RDF knowledge bases. These include taxonomy and hierarchy browsing (e.g. via SKOS taxonomies or the class hierarchy), facet-based browsing (with complex lter conditions and attribute based tag clouds) and full1The feature list is far away from being complete, so please refer http://ontowiki.net (for end-user centred functionality and screen-casts) and http://code.google.com/p/ ontowiki/ (for administration features and extensibility as well as development information) for a more complete view on our application. text search. These di erent navigation facilities can also be used as a combined navigation, for example a user can start with a full-text search and re ne the results using faceted-search or restrict them to a certain part of the selected hierarchy. OntoWiki translates these di erent navigation features into a single SPARQL query. In addition to rendering the results of such a query as a resource list, OntoWiki provides an extension mechanism for implementing dedicated views like maps and calendars. Once a speci c entity has been selected, the resource view displays all available information for that entity. Besides rendering this information generically in a tabular way, OntoWiki can be extended with domain speci c resource views (i.e. vocabulary). Speci c resource views for the SKOS and FOAF vocabularies are already included. Figure 1 shows the domain-independent list and resource view of OntoWiki.
All views in OntoWiki can be equipped with corresponding
RDFa annotations. OntoWiki employs the RDFauthor
mechanism [
In addition to this, the integration of RDFauthor as our main authoring mechanism led to two additional usage options:
By using OntoWiki's RDFauthor bookmarklet, users can collect data from di erent web pages and import it directly into their personal knowledge bases (e.g. contacts or events).
OntoWiki can be used as a service for hosting editable mash-ups. These mash-ups use data from OntoWiki's SPARQL endpoint and other data sources (which are interpreted as named graphs) and provide a merged view on this data. The bookmarklet is able to distinguish the statements from these named graphs and allow the user to edit these data directly inside the mash-up as well as to propagate the changes back
to the di erent sources (please refer to [
OntoWiki tries to support the creation of RDF Knowledge Bases from the scratch (rather than using prede ned ontologies only) in a wiki way. This means that our users often follow the learning by doing path, where requirements and priorities change over time. Our evolution framework allow OntoWiki users to apply prede ned evolution pattern from a pattern repository to their data, as well as to create their own pattern in order maintain the data quality of their Knowledge Base with little e ort. Examples for such evolution patterns include the splitting of classes by using their property values or the transition from a data property to an object property (e.g. the transition from literal based tags to resource based tags).
OntoWiki acts as a Linked Data server as well as an Linked Data client. Entities that use identi ers being governed by the OntoWiki installation are automatically served as Linked Data. OntoWiki supports access control on Linked Data employing the FOAF+SSL protocol as well as traditional local account based authentication. References to entities using foreign identi ers can be dereferenced (i.e. consumed by OntoWiki) in order to obtain additional information from the original source. Even non-linked data resources can be consumed by utilising speci c data-wrapper, that allow the generation of RDF data (e.g. from images, videos or web services).
Often it is bene cial for the owner of a Linked Data resource to be informed about the usage of their resources. When publishing a FOAF pro le, for example, it is useful to get noti ed when others establish a foaf:knows relation. We therefore developed the Semantic Pingback protocol. By employing Semantic Pingback, OntoWiki users can communicate RDF statements across domains and applications. 2.