File catalog

The reserved sparqld: graph describes the served directory. It lets queries relate data to the files and directories from which it came.

Resource	RDF types	Properties
Served directory	nfo:FileDataObject, nfo:Folder	nfo:fileName
Nested directory	nfo:FileDataObject, nfo:Folder	nfo:fileName, nfo:belongsToContainer
Source file with embedded graphs	nfo:FileDataObject, sd:Dataset	nfo:fileName, nfo:belongsToContainer, sd:namedGraph
Named-graph description	sd:NamedGraph	sd:name
Load error	rlog:Entry	rlog:resource

The source resource IRI is also its named graph IRI. The catalog is updated when source files are created, moved, or deleted.

Embedded graphs

For every embedded graph, the catalog uses sd:namedGraph to link the source dataset to an sd:NamedGraph description. Its sd:name is the scoped graph IRI. This is the SPARQL Service Description vocabulary's specific model for named graphs in a dataset.

flowchart TB root["Served directory"] folder["Subdirectory"] source["Source file"] description["Named-graph description"] scoped["Scoped graph IRI"] error["Load error"] folder -->|belongs to container| root source -->|belongs to container| folder source -->|has named graph| description description -->|names| scoped error -->|records resource| source

Query the catalog

This query lists every source file and its declared embedded graphs. A source without embedded graphs has an empty ?graph value.

Source file-catalog.rq

PREFIX nfo: <http://www.semanticdesktop.org/ontologies/2007/03/22/nfo#>
PREFIX sd: <http://www.w3.org/ns/sparql-service-description#>

SELECT ?file ?name ?directory ?graph
WHERE {
  GRAPH <sparqld:> {
    ?file a nfo:FileDataObject ;
          nfo:fileName ?name ;
          nfo:belongsToContainer ?directory .
    OPTIONAL {
      ?file sd:namedGraph [ sd:name ?graph ] .
    }
  }
}