The URIs have one of two forms:
where d is a digit.
In the second case, the identifiers denote the class of proteins that the UniProt accession is about. PRO uses these identifiers for the gene-organism level terms, and is considering using them for the isoform terms.
Response to access requests to PURLs
http://purl.obolibrary.org/obo/PR_.... represents a class defined in PRO, which isn't itself retrievable (protein classes can't be transmitted over wires) and so redirects (303) toto
http://purl.obolibrary.org/obo/pr/about/PR_.... which then links to the descriptive page about that protein class provided by the PRO project.
In addition, we define PURLs to directly access RDF for a term, as an intermediate solution on the way to having the PRO server offer the same protocol as the Ontobee server. These PURLs will redirect to OntoBee formatted RDF/XML
http://purl.obolibrary.org/obo/pr.owl is the latest released version of the Protein Ontology in OWL 2 RDF/XML syntax. This is the reasoned-over version, one which has all the additional axioms that are inferred from the original edited ontology.
http://purl.obolibrary.org/obo/pr.obo is the latest released version of the Protein Ontology in OBO format.
http://purl.obolibrary.org/obo/pr/yyyy-mm-dd/pr.owl is the version of the Protein Ontology in OWL 2 RDF/XML syntax that was released on day number dd of month number mm of the year yyyy. If you access that ontology you will find the ontologyIRI is
http://purl.obolibrary.org/obo/pr.owl and the versionIRI is
http://purl.obolibrary.org/obo/pr/yyyy-mm-dd/pr.owl owl These versions can be counted on to be stable even when new versions are released and projects that manage change carefully will want to import a specific version of PR.
http://purl.obolibrary.org/obo/pr/yyyy-mm-dd/pr.obo is the version of the Protein Ontology in OBO format that was released on day number dd of month number mm of the year yyyy.
http://purl.obolibrary.org/obo/pr/pr-asserted.owl is the asserted, or edited version of the latest release of PRO.
http://purl.obolibrary.org/obo/pr/yyyy-mm-dd/pr-asserted.owl is the asserted version of PRO, in OWL 2 RDF/XML syntax, released on yyyy-mm-dd
http://purl.obolibrary.org/obo/pr/yyyy-mm-dd/pr-asserted.obo is the asserted version of PRO, in OBO format, released on yyyy-mm-dd
http://purl.obolibrary.org/obo/pr/pr-dev.owl is the current development version (asserted) of PRO in OWL. This file may change day to day, and might even be broken. If you use it, understand the caveats.
http://purl.obolibrary.org/obo/pr/pr-dev.obo is the current development version (asserted) of PRO in OBO. This file may change day to day, and might even be broken. If you use it, understand the caveats.
Other project related PURLs
http://purl.obolibrary.org/obo/pr points to the PRO Project Home Page
http://purl.obolibrary.org/obo/pr/repository points to the browseable repository (currently at google code)
http://purl.obolibrary.org/obo/pr/wiki points to the pro wiki (on which this page is kept)
http://purl.obolibrary.org/obo/pr/browse points the PRO ontology browseable using OntoBee
http://purl.obolibrary.org/obo/pr/tracker points the PRO ontology issue tracker