Each xanadoc consists of one or more EDL sections. The EDL can contain
span pointers to source documents and links.
Each link is stored in a file with a permanent address. The link can contain
multiple facets, the number of facets depends on the type of link, for
example:
- italics: 1 facet
- title: 2 facets
- comments: 2 facets
Each item in a facet can be a sourcedoc, a xanadoc, a link or a span pointer.
span: