1.2 is clearer than 1.1 on this.

In 1.2, only entities that meet both of the following criteria are considered data entities:

• @type is File or Dataset
• @id is an absolute URI or a relative URI

#211 (comment)

The "determining which entities are data entities" thing will require major changes, especially in the way an existing RO-Crate is read: now entities are considered data entities if and only if they are referenced directly or indirectly (through Dataset instances, see #216) from the RDE's hasPart.

Thinking about implementation, should we split the behavior of ro-crate-py between 1.1 and 1.2 - i.e. retain the existing behaviour for 1.1 for consistency, and only implement the new behaviour for 1.2? I think we probably should.