default prefix without using base/BASE in turtle document

hi,

is there a way to write a turtle document that uses its own location as the
base prefix?

say on the server i have:

<base_url>/doc.ttl
<base_url>/some_file

is there a specification in the language that allows the following
statement in the doc.ttl file

:id :location <some_file>

to expand to:

:id :location <base_url>/some_file

without having the *base* keyword in the document.

basically i'm looking for a way to use relative IRIs such that doc.ttl and
some_file can be moved to any server and still be linked to each other
through the graph.

according to this:

http://www.w3.org/TR/turtle/#relative-iri

it looks like the specification of base is mandatory.

cheers,

satra