You can now retrieve a snapshot in time of the RDF or XSD serialization of a Concept/Scheme/Vocabulary by appending a ‘TimeSlice’ to the URI. For example: http://metadataregistry.org/uri/NSDLEdLvl/ts/20060422200002.rdf or http://metadataregistry.org/uri/NSDLEdLvl/ts/20060422200002.xsd will always and forever retrieve the SKOS/RDF or XML Schema representation of the NSDL Ed Level Vocabulary as it appeared at 2 seconds after 8PM on April 22, 2006 (2006-04-22 20:00:02). If you follow the above .rdf link you’ll notice that the concept URIs that the TimeSliced Vocabulary references have also had a TimeSlice appended: http://metadataregistry.org/uri/NSDLEdLvl/1001/ts/20060422200002.rdf in order to lock them into that precise point in time on an individual basis as well. We hope the utility of being able to reference a vocabulary at a particular point in time regardless of subsequent changes will be, well, useful.In order to make retrieving TimeSlices for specific events in the history of a vocabulary a bit handier, we added a TimeSlice link to every history event. You can specify a TimeSlice for any point in time regardless of its relationship to a history event, but the link just makes it simpler (it’s over on the right side of each line):

Uploaded with plasq’s Skitch!

Named Versions

You’ll maybe also have noticed that there’s a ‘Name’ link nestled to the right of the RDF and XSD links. If you’re a Vocabulary Administrator, then you now have the ability to label a TimeSlice with a distinct version name. That link again is there to make it easy to reference a point in historical time and clicking on it pre-enters that TimeSlice into the Create new version form:

Uploaded with plasq’s Skitch!There’s no limit to the number of versions you can create, and versions (unlike TimeSlices) can be deleted or edited by any Vocabulary Admin:

Uploaded with plasq’s Skitch!…although we think that either editing or deleting a version is likely to be a less-than-ideal practice. Still, we allow it — it’s your vocabulary after all.Once a named version has been associated with a TimeSlice, it will appear in the event history list just above the point in time it references:

Uploaded with plasq’s Skitch!The RDF and XSD links on the right side of the version line now reference the version name:http://metadataregistry.org/uri/NSDLEdLvl/version/release+1.0.rdfBut this is where it gets a little incorrect… Since the named version URL is just a TimeSlice reference, it does a silent redirect to the referenced TimeSlice. It should probably do a 303 redirect instead. We’ll fix this later, unless it’s a show-stopper for one of our many users.