Sending an HTTP GET request to a media resource on an Alph server with a "describe" query parameter returns a JSON-LD response document containing metadata about the resource.
OTHER INTERFACES
These response documents are also available by sending an HTTP GET request with the "Accept" header set to one of these media types:
application/ld+json
application/n-triples
application/rdf+xml
text/n3
text/turtle
The response document will, of course, be in the requested format.
VOCABULARY
Alph uses the Schema.org vocabulary for authorship, licensing, and other metadata properties, and classifies all media resources as the Schema.org "MediaObject" type. Additional Alph-specific properties/relations are defined at <http://alph.io/terms>. Other servers implementing this interface are more than welcome to use additional/alternative vocabularies, of course.
UPDATING RESOURCE METADATA
The ?describe interface is also used by the Alph server to modify the LD representation of a resource. For the specifics on that, try <http://alph.io/alph.py/api>