Ghost Nodes

Fedora 6.x.x introduced the concept of "ghost nodes". These are URI path segments that do not resolve to a resource on their own.

For example, in a new empty repository:

curl -v -XPUT http://localhost:8080/rest/ghost/path/object

would create a single resource at the path /rest/ghost/path/object

> curl -i -ufedoraAdmin:fedoraAdmin http://localhost:8080/rest/ghost/newThing     
HTTP/1.1 200 OK
Date: Mon, 10 Apr 2023 18:01:26 GMT
Set-Cookie: JSESSIONID=node0ppsmswh9fma1lnqa042y0hkp9.node0; Path=/
Expires: Thu, 01 Jan 1970 00:00:00 GMT
Set-Cookie: rememberMe=deleteMe; Path=/; Max-Age=0; Expires=Sun, 09-Apr-2023 18:01:26 GMT; SameSite=lax
ETag: W/"C0B283FE60C11A3E7943963799EE7A10"
X-State-Token: 21217075951D35683BA87AE42580C2BF
Last-Modified: Mon, 10 Apr 2023 18:00:50 GMT
Link: <http://localhost:8080/rest/ghost/newThing>; rel="timegate"
Link: <http://localhost:8080/rest/ghost/newThing>; rel="original"
Link: <http://localhost:8080/rest/ghost/newThing/fcr:versions>; rel="timemap"
Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel="type"
Link: <http://www.w3.org/ns/ldp#Resource>; rel="type"
Link: <http://fedora.info/definitions/v4/repository#Resource>; rel="type"
Link: <http://mementoweb.org/ns#OriginalResource>; rel="type"
Link: <http://mementoweb.org/ns#TimeGate>; rel="type"
Link: <http://www.w3.org/ns/ldp#RDFSource>; rel="type"
Link: <http://www.w3.org/ns/ldp#Container>; rel="type"
Link: <http://fedora.info/definitions/v4/repository#Container>; rel="type"
Accept-External-Content-Handling: copy,redirect,proxy
Accept-Patch: application/sparql-update
Accept-Post: text/turtle,text/rdf+n3,text/n3,application/rdf+xml,application/n-triples,application/ld+json
Allow: DELETE,POST,HEAD,GET,PUT,PATCH,OPTIONS
Link: <http://localhost:8080/rest/ghost/newThing/fcr:acl>; rel="acl"
Preference-Applied: return=representation
Vary: Prefer
Vary: Accept
Vary: Range
Vary: Accept-Encoding
Vary: Accept-Language
Vary: Accept-Datetime
Content-Type: text/turtle;charset=utf-8
Content-Length: 816
Server: Jetty(9.4.44.v20210927)

@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix fedora: <http://fedora.info/definitions/v4/repository#> .
@prefix ldp: <http://www.w3.org/ns/ldp#> .

<http://localhost:8080/rest/ghost/newThing>
        fedora:created         "2023-04-10T18:00:50.202420Z"^^<http://www.w3.org/2001/XMLSchema#dateTime> ;
        fedora:lastModified    "2023-04-10T18:00:50.202420Z"^^<http://www.w3.org/2001/XMLSchema#dateTime> ;
        fedora:createdBy       "fedoraAdmin" ;
        fedora:lastModifiedBy  "fedoraAdmin" ;
        rdf:type               ldp:BasicContainer ;
        rdf:type               ldp:Resource ;
        rdf:type               fedora:Resource ;
        rdf:type               ldp:RDFSource ;
        rdf:type               ldp:Container ;
        rdf:type               fedora:Container .

The paths http://localhost:8080/rest/ghost and http://localhost:8080/rest/ghost/path both return a 404 Not Found for requests.

> curl -i -ufedoraAdmin:fedoraAdmin http://localhost:8080/rest/ghost         
HTTP/1.1 404 Not Found
Date: Mon, 10 Apr 2023 18:01:30 GMT
Set-Cookie: JSESSIONID=node0evxhuptudzd010yslilwp5pu010.node0; Path=/
Expires: Thu, 01 Jan 1970 00:00:00 GMT
Set-Cookie: rememberMe=deleteMe; Path=/; Max-Age=0; Expires=Sun, 09-Apr-2023 18:01:30 GMT; SameSite=lax
Content-Type: text/turtle;charset=utf-8
Content-Length: 32
Server: Jetty(9.4.44.v20210927)

Error: Resource /ghost not found

> curl -i -ufedoraAdmin:fedoraAdmin http://localhost:8080/rest/ghost/path
HTTP/1.1 404 Not Found
Date: Mon, 10 Apr 2023 17:57:18 GMT
Set-Cookie: JSESSIONID=node01jeiv46h6xn6h1peerv0d3zp5l5.node0; Path=/
Expires: Thu, 01 Jan 1970 00:00:00 GMT
Set-Cookie: rememberMe=deleteMe; Path=/; Max-Age=0; Expires=Sun, 09-Apr-2023 17:57:18 GMT; SameSite=lax
Content-Type: text/turtle;charset=utf-8
Content-Length: 37
Server: Jetty(9.4.44.v20210927)

Error: Resource /ghost/path not found

These are called "ghost" nodes because they still have a haunting effect. You cannot replace these path segments with a new resource. This is a significant difference from Fedora 4.x & 5.x

> curl -i -ufedoraAdmin:fedoraAdmin http://localhost:8080/rest/ghost -XPUT              
HTTP/1.1 409 Conflict
Date: Mon, 10 Apr 2023 18:05:05 GMT
Set-Cookie: JSESSIONID=node01i26p8o44mumkrmixiobx8zf718.node0; Path=/
Expires: Thu, 01 Jan 1970 00:00:00 GMT
Set-Cookie: rememberMe=deleteMe; Path=/; Max-Age=0; Expires=Sun, 09-Apr-2023 18:05:05 GMT; SameSite=lax
Content-Type: text/plain;charset=utf-8
Content-Length: 45
Server: Jetty(9.4.44.v20210927)

Resource path ghost is an immutable resource.

> curl -i -ufedoraAdmin:fedoraAdmin http://localhost:8080/rest/ghost/path -XPUT
HTTP/1.1 409 Conflict
Date: Mon, 10 Apr 2023 18:03:42 GMT
Set-Cookie: JSESSIONID=node013j2yecnv6mis8pb8dc60qyjm14.node0; Path=/
Expires: Thu, 01 Jan 1970 00:00:00 GMT
Set-Cookie: rememberMe=deleteMe; Path=/; Max-Age=0; Expires=Sun, 09-Apr-2023 18:03:42 GMT; SameSite=lax
Content-Type: text/plain;charset=utf-8
Content-Length: 50
Server: Jetty(9.4.44.v20210927)

Resource path ghost/path is an immutable resource.

You can create items off part of the "ghost" path segments.

> curl -i -ufedoraAdmin:fedoraAdmin -XPUT http://localhost:8080/rest/ghost/newThing1 
HTTP/1.1 201 Created
Date: Mon, 10 Apr 2023 18:00:50 GMT
...

http://localhost:8080/rest/ghost/newThing1

> curl -i -ufedoraAdmin:fedoraAdmin http://localhost:8080/rest/ghost/newThing1
HTTP/1.1 200 OK
Date: Mon, 10 Apr 2023 18:06:54 GMT

You can also create other resources at the same level as the original resource.

> curl -i -ufedoraAdmin:fedoraAdmin http://localhost:8080/rest/ghost/path/newThing2 -XPUT
HTTP/1.1 201 Created
Date: Mon, 10 Apr 2023 18:04:02 GMT
...

http://localhost:8080/rest/ghost/path/newThing2

> curl -i -ufedoraAdmin:fedoraAdmin http://localhost:8080/rest/ghost/path/newThing2     
HTTP/1.1 200 OK
Date: Mon, 10 Apr 2023 18:04:06 GMT

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Ghost Nodes