University of Malta
Department of Computer Science and Artificial Intelligence
The Semantic Web as visualized by Tim Berners Lee will be the keystone in the creation of machine accessible domains of information scattered around the globe. All information on the World Wide Web would be semantically enhanced with information that makes sense to intelligent information agents through the use of the Resource Description Framework (RDF) and the associated Schema Language (RDFS). Being specific information describing the contents of web documents, this hidden metadata deserves worthy attention and a means to present it to web users. This information should also lead to more accessible data. In the semantic web, classes of objects and their relationships are described in accessible Ontologies. In turn, resources in a web document are defined as instances of the objects in the applicable Ontologies. Creating relationships between the resources is possible with the use of the OWL language, a Web Ontology Language that is built on top of RDF/RDFS and XML. The ultimate goal of the Semantic Web is to achieve a semantically enabled world wide web, by annotating each and every online document and service with semantic meaning. In this way it will be possible to relate between every defined object on the web and make it easier for agents to understand the content of the web, and ultimately for people to have easier access to concept-oriented data.
Web Page annotation, using domain specific ontologies is the basis of the semantic web, and besides RDF and RDFS, OWL has emerged as the most common language for defining relationships between resources in a web page. A Semantic Web Browser will deal with the annotations embedded in the Head of the HTML of a web page.
Currently there are two approaches to creating Semantic Web Browsers. A Semantic Web Browser has been described (in a paper discussing semantic web browsers in relation with Haystack project) as a browser that explores the semantic web in its own right, and is able to relate and aggregate information about resources located in different web documents. On the other hand a Semantic Web Browser can be described as a special web browser, that augments standard web browsers with the ability to visualize hidden metadata. While approaches like the latter would be based almost entirely on the present WWW resource sharing technologies, other approaches could involve new ideas. In particular, special repositories could collect RDF triples from various accessed locations over time. Such triple stores could largely improve the efficiency of locating information on some resource of interest.
|semantExplorer is based on the following
semantExplorer attempts to bridge the gap between the 'Semantic Web Browser' and 'Semantic Web Browser' approaches. While the Table and Graph Builders contribute to the 'Semantic Web Browser', the Lens Builder, by enabling navigation to related data, contributes to the alternate approach.
|semantExplorer includes a
Navigation Panel ( Back, Forward, Stop, Refresh and the Address Bar ) that
provides standard document navigation for '.html' web pages, and '.rdf'
and '.owl' ontologies.
Once a document is loaded successfully, any RDF content is extracted and parsed. Resources described through this metadata are listed in the 'Defined Objects' List. In the case of Ontologies, defined classes and properties will also be listed.
The browser includes four views:
Triples can sometimes be difficult to interpret. Many times, a group of triples relating to a single item will include a number of blank nodes, particularly when using RDF lists (rdf:Bag etc) and OWL complex classes. semantExplorer caters for this problem by providing the possibility to process the triples for such RDF/RDFS and OWL constructs to remove blank nodes. As an example, when parsing data describing that some university department has an 'AcademicStaff' consisting of ten academics, parsers will generate 12 triples, 10 of which will have blank nodes as their subject. With these RDF/RDFS/OWL fixes, such a statement will be reduced to just one line. Another option, Tag Fix, enables resources to be capitalized and namespaces to be hidden. Furthermore, in the case of the Lens and Graph Viewers, since many times graphs will include information that is irrelevant to the average user (for example that 'SimonScerri' is an owl:Thing, or that 'Student' is an rdfs:Class), another option will hide such constructs.
Once a resource has been navigated to, it can be saved as a Collection, much like favourites are stored in standard web browsers. They are called collections since once they are re-selected and navigated to, the web browser, item description and graph viewer will provide information on the resource, while the lens viewer will aggregate data that is known to be related to the selected resource. Such collections can be added, modified or deleted. semantExplorer also include local caching of visited locations, to speed up navigation. Such caching will include both the source of the document as well as its RDF parse files, if any. This cache can be turned off or set to a custom limit.
Other Screen shots
semantExplorer has been implemented using the .NET framework and the C# language, thus proving that the Semantic Web does not entirely belong to Java. It is an ongoing project and the first version will soon be available for download together with a user manual. Like all applications, semantExplorer has it's limitations. In particular, RDF data needs to be annotated inline in the document or via an anchor link to an RDF file. The application caters for RDF,RDFS and OWL languages. Other languages (e.g.. DAML) will not be recognized. Such data will only be extracted from .html , .rdf and .owl documents/ontologies. Transfer Protocol should be the hypertext protocol HTTP.
Proposed future work will include the improvement of cache file generation and the inclusion of a reasoner within the Lens builder.
A user manual for semantExplorer is provided here.
semantExplorer: A Semantic Web Browser, Simon Scerri, Charlie Abela, Matthew Montebello, accepted at the IADIS International Conference WWW/Internet 2005, Lisbon Portugal, October 2005 (pdf)
Any queries and/or suggestions regarding this tool are more
than welcome and can be e-mailed to: