On 08/05/13 02:28, Owen Stephens wrote:

> 1) A highlighted span of text.  There is an obvious target segment of a
> resource (the object), but there is no body/comment (the subject).  As a
> triple must have a subject, this could not be expressed.  A second
> example of this would be a bookmark where the body is also implicit.

I'm not quite sure what you mean by "could not be expressed" Such use 
cases are readily expressed using the XPointer family of schemes. The 
best introduction to them I'm aware of is at Members of the family exists in 
a variety of states of implementation and standardisation.

> 2) An annotation that refers to multiple segments of a resource,
> multiple resources or multiple segments of multiple resources.  In this
> case there would be multiple objects, which is also not possible to be
> expressed in RDF.

The W3C XPointer scheme at can point 
to any set of things pointable to by a single XPath 1.0 expression.

I have to admit that XPointer is not widely used with the RDF / linked 
data. I'd have to take the advice of those with more linked data 
experience as to whether using them in combination is wise.

Stuart Yeates
Library Technology Services