Reference fragmentation

Reference fragmentation will create fragments based on a provided property path defined as tree:fragmentationPath. When no fragmentationPath is defined, “rdf:type” is used by default. A tree:fragmentationKey can be used to customize the request parameter key. This is useful when nesting multiple reference fragmentations. You can have a fragment that looks like this http://{hostname}/{collection}/{view}?type={a-type}&version={a-version}. This allows you to fragment the data on references.

Properties 

@prefix tree: <https://w3id.org/tree#> .

tree:fragmentationStrategy [
     a tree:ReferenceFragmentation ;
     tree:fragmentationPath { Optional: defines which property will be used for bucketizing } ;
     tree:fragmentationKey { Optional: defines the request parameter that will be used in the uri } ;
 ] .

Algorithm

  1. The fragmentationObjects of the member are determined
    • We filter the RDF statements where the property path matches the fragmentationPath
    • We select all the object that pass the above filters.
  2. A bucket of references is created using the object value(s)
  3. The buckets are iterated. The member is added to every bucket. Taking into account:
    • A new fragment is created if no fragment exists for the given reference.
    • The member is added to every related fragment
  4. When the member could not be added to any bucket (ex. the fragmentation property is missing or not valid), then the member will be added to a default bucket key=unknown.

Example

Example properties:

@prefix tree: <https://w3id.org/tree#> .

tree:fragmentationStrategy [
     a tree:ReferenceFragmentation ;
     tree:fragmentationPath "<http://purl.org/dc/terms/isVersionOf>" ;
     tree:fragmentationKey "version" ;
 ] .

With following example input:

@prefix dc: <http://purl.org/dc/terms/> .
@prefix ns0: <http://semweb.mmlab.be/ns/linkedconnections#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix ns1: <http://vocab.gtfs.org/terms#> .
@prefix prov: <http://www.w3.org/ns/prov#> .
@prefix ns2: <http://www.opengis.net/ont/geosparql#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix geo: <http://www.w3.org/2003/01/geo/wgs84_pos#> .

<http://njh.me/original-id/123#2022-09-28T17:11:28.520Z>
  dc:isVersionOf <http://njh.me/original-id/123> ;
  ns0:arrivalStop <http://example.org/stops/402161> ;
  ns0:arrivalTime "2022-09-28T07:14:00.000Z"^^xsd:dateTime ;
  ns0:departureStop <http://example.org/stops/402303> ;
  ns0:departureTime "2022-09-28T07:09:00.000Z"^^xsd:dateTime ;
  ns1:dropOffType ns1:Regular ;
  ns1:pickupType ns1:Regular ;
  ns1:route <http://example.org/routes/Hasselt_-_Genk> ;
  ns1:trip <http://example.org/trips/Hasselt_-_Genk/Genk_-_Hasselt/20220928T0909> ;
  a ns0:Connection ;
  prov:generatedAtTime "2022-09-28T17:11:28.520Z"^^xsd:dateTime .

The selected object would be

<http://njh.me/original-id/123>

After ingestion the member will be part of the following fragment

NOTE: “version” is based on the configuration property “tree:fragmentationKey”.