It is obvious that not all the pitfalls are equally important; their impact in the ontology will depend on multiple factors. For this reason, each pitfall has an importance level attached indicating how important it is. We have identified three levels:
Guidelines in  suggest avoiding file extension in persistent URIs, particularly those related to the technology used, as for example ".php" or ".py". In our case we have adapted it to the ontology web languages used to formalized ontologies and their serializations. In this regard, we consider as pitfall including file extensions as ".owl", ".rdf", ".ttl", ".n3" and ".rdfxml" in an ontology URI. An example of this pitfall (at 29th June, 2012) could be found in the "BioPAX Level 3 ontology (biopax)" ontologyÃ•s URI (http://www.biopax.org/release/biopax-level3.owl) that contains the extension ".owl" related to the technology used.
*This pitfall applies to the ontology in general instead of specific elements and it appears in the ontology URI: http://casas.wsu.edu/owl/cose.owl
It is crucial you solve this if you want to contribute to the Semantic Web. You can follow the guidelines at LinkToDiegoRecipes to publish your ontology. If your ontology is correctly published and we have made an error detecting this pitfall please let us know and we will solve it a.s.a.p.
*This pitfall applies to the ontology in general instead of specific elements