Abstract. Semantic Web applications take off is being slower than expected, at least with respect to "real-world" applications and users. One of the main reasons for this lack of adoption is that most Semantic Web user interfaces are still immature from the usability and accessibility points of view. This is due to the novelty of these technologies, but this also motivates the exploration of alternative interaction paradigms, different from the "traditional" Web or Desktop applications ones. Our proposal is realized in the Rhizomer platform, which explores the possibilities of the object-action interaction paradigm at the Web scale. This paradigm is well suited for heterogeneous resource spaces such as those common in the Semantic Web.Resources, described by metadata, correspond to the objects in the paradigm.Semantic web services, which are dynamically associated to these objects, correspond to the actions. The platform is being put into practice in the context of a research project in order to build an open application for media distribution based on Semantic Web technologies. Moreover, its usability and accessibility have been evaluated in this real setting and compared to similar systems.

The Rhizomer platform is a Content Management System (CMS) based on a Resource Oriented Approach (RESTful) and Semantic Web technologies. It achieves a great level of flexibility and provides sophisticated content management services. All content is described using semantic metadata semi-automatically extracted from multimedia content, which enriches the browsing experience and enables semantic queries. A usable user interface is built on top of the CMS in order to facilitate the interaction with content and enhance it with the information provided by the associated semantic metadata. As an application scenario of the platform, its use in a media company where audio content is managed and its speech transcript semantically annotated is described.

In order to make a Semantic Web dataset more usable to a wider range of users, specially Linked Data ones, Rhizomer constitutes a tool for data publishing in the web that in addition to common data browsing mechanisms based on HTML rendering, provides a set of components that facilitate awareness of the dataset at hand borrowed from Information Architecture. Rhizomer automatically generates navigation menus taking into account the ontologies used by the dataset and facets based on how properties are instantiated for each of the classes in the dataset. This makes it possible for users to easily be aware of the main kinds of things in the dataset but also their main properties and the values the take while they perform faceted navigation. These generic IA components are complemented with specialised interaction services that can be dynamically deployed and associated to resource using semantic web services. Among these services, Rhizomer features one that provides simple edition of the data using autocomplete forms guided by the ontologies used in the dataset and the available resources.

Semantic Web applications tests show that their usability is seriously compromised. This motivates the exploration of alternative interaction paradigms, different from the "traditional" Web or desktop applications ones. The Rhizomer platform is based on the object-action interaction paradigm, which is better suited for heterogeneous resource spaces such as those common in the Semantic Web. Resources, described by means of RDF metadata, correspond to the objects from the interaction point of view and Rhizomer provides browsing mechanisms for them. Semantic web services, dynamically associated to these objects, correspond to the actions. Rhizomer has been applied in the context of a media house to build an audiovisual content management system. End-users of this system, journalists and archivists, are able to navigate the content repository through semantic metadata describing content pieces and the domain knowledge these pieces are referring to. Those resources constitute the objects to which, when the user selects one of them, semantic web services dynamically associate specialized visualization and interaction views, the actions.

No abstract