To enhance the treatment of relations in biomedical ontologies we advance a methodology for providing consistent and unambiguous formal definitions of the relational expressions used in such ontologies in a way designed to assist developers and users in avoiding errors in coding and annotation. The resulting Relation Ontology can promote interoperability of ontologies and support new types of automated reasoning about the spatial and temporal dimensions of biological and medical phenomena.

This paper presents use cases for modular development of ontologies using the OWL imports mechanism. Many of the methods are inspired by work in modular development in software engineering. The approach is aimed at developers of large ontologies covering multiple subdomains that make use of OWL reasoners for inference. Such ontologies are common in biomedical sciences, but nothing in the paper is specific to biomedicine. There are four groups of use cases: (i) organisation and factoring of ontologies; (ii) maintaining stable (...) interfaces and bindings between ontologies and between ontologies and software; (iii) localization of ontologies to the requirements of specific sites and (iv) extension of ontologies and encapsulation of modifications. OWL's axiom-oriented import mechanism has many similarities with import mechanisms in object-oriented software but also important differences – in particular, the effects of OWL imports are global, and the order in which modules are imported is irrelevant. The advantages and disadvantages of OWL's axiom-oriented approach are discussed, and suggestions are made for extensions to allow axioms to be filtered out as well as added – a mechanism that we term “adaptation” to distinguish it from the standard import mechanism. Finally we discuss possible alternatives and practical experience with the approaches presented. (shrink)