Cultural heritage is encoded in a variety of forms. The task of preserving heritage involves preserving the tangible and intangible resources that broadly define that heritage. A significant aspect of intangible heritage resources are performing arts which include classical dance and music. Digital heritage resources include heritage artefacts in digitized form as well as the background knowledge that puts them in perspective. We present an ontology based approach to capture and preserve the knowledge with digital heritage artefacts. Since the artefacts are generally preserved in multimedia format, we propose the use of Multimedia Web Ontology (MOWL) that supports probabilistic reasoning with media properties of domain concepts, to encode the domain knowledge. We propose an architectural framework that includes a method to construct the ontology with a labelled set of training data and use of the ontology to automatically annotate new instances of digital heritage artefacts. The annotations enable creation of a semantic navigation environment in a cultural heritage repository. We have realized a proof of concept in the domain of Indian Classical Dance and present some results.