1 InfixOWL: An Idiomatic Interface for OWL Chimezie Ogbuji, Cleveland Clinic Foundation Heart and Vascular Institute <ogbujic@ccf.org> Abstract The Ontology Web Language (OWL) provides a powerful framework for describing the semantics and constraints of a particular domain described in RDF. Along with that power comes the burden of a learning curve that is often inherited by the tools used to manage OWL ontologies. The Manchester OWL syntax introduced an intuitive syntax for the presentation and editing of OWL ontologies that attempted to address some of this burden for the benefit of authors. One of the major design decisions of this syntax was the adoption of an infix notation. The primary contribution of this paper is a native, idiomatic API for constructing and manipulating OWL in Python that builds on the strengths of the Manchester OWL syntax. It is called InfixOWL. Introduction The Ontology Web Language is a Description Logic (DL) dialect for the Semantic Web [SW]. DLs are decidable subsets of First Order Logic that have a tree-like model [DL2OWL]. When modeling reality in the classical paradigm [SW-Modeling], the domain being modelled is abstractly represented as a set of objects with relationships between them. Ontologies consist of sets of axioms that describe required characteristics of the domain expert's understanding of the world. An ontology corresponds to a logical theory. This requires a certain level of sophistication in the knowledge representation that can be problematic for editing tools and the readability of OWL document. Readability of OWL Generally, the canonical serialization of OWL (RDF/XML) suffers from the same impedance to readability that RDF graphs do. RDF/XML has been shown by many to be cumbersome to manage and read. The standard representational forms for OWL are not suitable for writing class expressions are either too verbose, or too complicated. [Man-OWL]. OWL can be considered a special-purpose language for modeling and reasoning about reality in a computationally tractable and expressive way. Given the nature of OWL as a language framework, it is very important that a reader of OWL syntax find the forms easily to understand without any disturbance from syntax. The concrete syntax used to capture OWL needs to make use of language idioms in order for them to be intuitive to domain experts. Readability of Manchester OWL The Manchester OWL syntax was designed as a simple, readable text format for expressing complex class descriptions. It was primarily intended for presenting such descriptions to (non-logician) human users. The focus was on allowing even relatively complex expressions to be readable as natural (English) language. Another major goal for this syntax was readability and a reduction in the amount of time it takes domain experts to understand class descriptions. A significant design decision for the Manchester OWL syntax