ldp:contains doesn't necessarly point to the focus node of Data Instance

[elf-pavlik]

In 5.2. Data Registration we find

Each Data Instance is linked via the ldp:contains property.

In cases where IRI denoting Data Instance has # fragment, ldp:contains will just link to the resource without the fragment.

I understand that we want to rely on the server to manage containment tripes. In that case we probably need to clarify that ldp:cotains links to the resource describing data instance and explain how do find focus node of that resource.

I'm going to update snippets in the primer and instead of having

alice-pro:773605f0-b5bf-4d46-878d-5c167eac8b5d
  a interop:DataRegistration ;
  # [...]
  interop:registeredShapeTree solidtrees:Project ;
  ldp:contains
    alice-pro:ccbd77ae-f769-4e07-b41f-5136501e13e7\#project ,
    alice-pro:7a130c38-668a-4775-821a-08b38f2306fb\#project .

have it without fragments

alice-pro:773605f0-b5bf-4d46-878d-5c167eac8b5d
  a interop:DataRegistration ;
  # [...]
  interop:registeredShapeTree solidtrees:Project ;
  ldp:contains
    alice-pro:ccbd77ae-f769-4e07-b41f-5136501e13e7 ,
    alice-pro:7a130c38-668a-4775-821a-08b38f2306fb .

Once I do that I will see where sai-js code breaks and where do we need to map resources to their focus nodes.