An Annotation Tool for Semantic Documents

Document annotation is a common technique for relating text and knowledge representation. Although the semantic web emphasizes the annotation of web pages, there are other types of documents that can benefit from ontology-based annotations. PDF documents combined with OWL ontologies form semantic documents that support professional printing, on-line viewing, and ontological models. PDFTab is an extension to the Protégé ontology editor that allows developers to annotate PDF documents with OWL-based ontologies. It is possible to add OWL ontologies to preexisting PDF documents and to relate document parts to concepts in the ontology. PDFTab integrates Adobe Acrobat with Protégé and allows users to switch seamlessly between the document and ontology views. PDFTab illustrates how it is possible to extend semantic-web techniques to the widely-used PDF format while maintaining strong support for ontology development and editing.