Ontology Verbalization using Semantic-Refinement

In this paper, we propose a rule-based technique to generate redundancy-free natural language (NL) descriptions of Web Ontology Language (OWL) entities. The existing approaches which address the problem of verbalizing OWL ontologies generate NL text segments which are close to their counterpart statements in the ontology. Some of these approaches also perform grouping and aggregating of these NL text segments to generate a more fluent and comprehensive form of the content. Restricting our attention to description of individuals and atomic concepts, we find that the approach currently followed in the available tools is that of determining the set of all logical conditions that are satisfied by the given individual/concept name and translate these conditions verbatim into corresponding NL descriptions. Human-understandability of such descriptions is affected by the presence of repetitions and redundancies, as they have high fidelity to the OWL representation of the entities. In the literature, no efforts had been taken to remove redundancies and repetitions at the logical level before generating the NL descriptions of entities and we find this to be the main reason for lack of readability of the generated text. In this paper, we propose a technique called semantic-refinement to generate meaningful and easily-understandable (what we call redundancy-free) text descriptions of individuals and concepts of a given OWL ontology. We identify the combinations of OWL/DL constructs that lead to repetitive/redundant descriptions and propose a series of refinement rules to rewrite the conditions that are satisfied by an individual/concept in a meaning-preserving manner. The reduced set of conditions are then employed for generating textual descriptions. Our experiments show that, semantic-refinement technique leads to significantly improved descriptions of ontology entities. We also test the effectiveness and usefulness of the the generated descriptions for the purpose of validating the ontologies and find that the proposed technique is indeed helpful in the context. The details of an empirical study to support the claim are provided in the paper.