Take for example the following:
http://www.ibiblio.org/maven/ant/jars/ant-1.5.jar http://www.ibiblio.org/maven/ant/jars/ant-1.5.jar.md5
You can express the above as:
<artifact-address>/<type>/<artifact-name>.<type>.<metadata>
This implies that there is a notion of meta-data down at the base level - in particular the schema through which meta-data is associated to an artifact.
or, the 'type' in the second instance is 'jar.md5' vs '.jar' for the first.
i don't think the md5 example is enough to warrant just treating the repository as a directory of files though..
-pete