fcrepo4_deltas.md 3.1 KB
Divergencies between lakesuperior and FCREPO4
Endpoints
The FCREPO root endpoint is /rest. The LAKEsuperior root endpoint is /ldp.
This should not pose a problem if a client does not have rest hard-coded in
its code, but in any event, the /rest endpoint is provided for backwards
compatibility.
LAKEsuperior adds the (currently stub) query endpoint. Other endpoints for
non-LDP services may be opened in the future.
Automatic pairtree generation
A POST request without a slug in FCREPO4 results in a pairtree consisting of
several intermediate nodes leading to the automatically minted identifier. E.g.
POST /rest
results in /rest/8c/9a/07/4e/8c9a074e-dda3-5256-ea30-eec2dd4fcf61 being
created.
The same request in LAKEsuperior would create
rest/8c9a074e-dda3-5256-ea30-eec2dd4fcf61 (obviously the identifiers will be
different).
Explicit intermediate paths
In FCREPO4, a PUT request to /rest/a/b/c, given /rest/a and rest/a/b not
previously existing, results in the creation of Pairtree resources that are
retrievable. In LAKEsuperior the same operation results only in the creation of
containment triple in the graph store, which are not exposed in the LDP API.
Therefore, a GET to rest/a in FCREPO4 will result in a 200, a GET to rest/a
in LAKEsuperior in a 404.
In both above cases, PUTting into rest/a yields a 409, POSTing to it results
in a 201.
Lenient handling
FCREPO4 requires server-managed triples to be expressly indicated in a PUT
request, unless the Prefer heeader is set to
handling=lenient; received="minimal", in which case the RDF payload must not
have any server-managed triples.
LAKEsuperior works under the assumption that client should never provide
server-managed triples. It automatically handles PUT requests sent to existing
resources by returning a 412 if any server managed triples are included in the
payload. This is the same as setting Prefer to handling=strict, which is
the default.
If Prefer is set to handling=lenient, all server-managed triples sent with
the payload are ignored.
Automatic LDP class assignment
Since LAKEsuperior rejects client-provided server-managed triples, and since
the LDP types are among them, the LDP container type is inferred from the
provided properties: if the ldp:hasMemberRelation and
ldp:membershipResource properties are provided, the resource is a Direct
Container. If in addition to these the ldp:insertedContentRelation property
is present, the resource is an Indirect Container. If any of the first two are
missing, the resource is a Container (@TODO discuss: shall it be a Basic
Contaner?)
LDP-NR metadata by content negotiation
FCREPO4 relies on the /fcr:metadata identifier to retrieve RDF metadata about
an LDP-NR. LAKEsuperior supports this as a legacy option, but encourages the
use of content negotiation to do that. Any request to an LDP-NR with an
Accept header set to one of the supported RDF serialization formats will
yield the RDF metadata of the resource instead of the binary contents.
Asynchronous processing
TODO
The server may reply with a 202 if the Prefer header is set to
respond-async.