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mappings.md

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Mapping to RDF

A link dump can be mapped to an RDF graph as described in this section. The mapping excludes all links with one of source identifier, target identifier, relation type not being a valid URI.

All URIs MUST be transformed to IRIs as defined in Section 3.2 of .

Examples of link dumps mapped to RDF are given in .

Naming conventions

The following namespace prefixes are used to refer to RDF properties and classes from the RDFS vocabulary , the DCMI Metadata Terms , the FOAF vocabulary , the VoID vocabulary , and the Hydra Core Vocabulary , the RSS 1.0 Syndication Module :

 rdfs:    <http://www.w3.org/2000/01/rdf-schema#>
 dcterms: <http://purl.org/dc/terms/>
 foaf:    <http://xmlns.com/foaf/0.1/>
 void:    <http://rdfs.org/ns/void#>
 hydra:   <http://www.w3.org/ns/hydra/core#>
 rssynd:  <http://web.resource.org/rss/1.0/modules/syndication/>

The blank node :dump denotes the the link dump, the blank node :sourceset denotes the the source dataset, and the blank node :targetset denotes the the target dataset. Source datatset and target datatset can also be given an absolute IRI with meta fields SOURCESET and TARGETSET, respectively ().

Default triples

The following RDF triples can always be assumed when mapping link dumps to RDF:

 :dump a void:Linkset, hydra:Collection ;
     void:subjectsTarget :sourceset ;
     void:objectsTarget :targetset .

 :sourceset a void:Dataset .
 :targetset a void:Dataset .

All publically available BEACON data dumps SHOULD be Open Data, so the following triple MAY be assumed as well:

:dump <http://creativecommons.org/ns#license>
    <http://creativecommons.org/publicdomain/zero/1.0/> .

Links in RDF

Links () with source identifier, target identifier, and relation type being valid URIs can be mapped to at least one RDF triple with:

  • the source identifier used as subject IRI,
  • the relation type used as predicate,
  • the target identifiers used as object IRI.

The total number of mappable links in a link dump SHOULD result in two additional RDF triples whith COUNT being the number of links:

 :dump hydra:totalItems COUNT .
 :dump void:entities COUNT .

Link annotations in RDF

Each non-empty link annotation SHOULD result in an additional RDF triple with:

  • the target identifier used as subject IRI,
  • the ANNOTATION meta field used as predicate,
  • the link annotation value used as literal object.

Applications MAY use a predefined IRI as link annotation or process the link annotation by other means, for instance for provenience and versioning of links. Applications MAY assign a default language tag or datatype to all literal objects derived from link annotations.

Typical use cases of link annotations include specification of labels and a "number of hits" at the target dataset. For instance the following file in BEACON format ():

 #PREFIX: http://example.org/
 #TARGET: http://example.com/
 #RELATION: http://xmlns.com/foaf/0.1/primaryTopic
 #ANNOTATION: http://purl.org/dc/terms/extent

 abc|12|xy

can be mapped to

 <http://example.org/abc> foaf:primaryTopic <http://example.com/xy> .
 <http://example.com/xy> dcterms:extent "12" .

The total number of mappable links and link annotations in a link dump SHOULD result in an additional RDF triple whith TRIPLES being the sum of both numbers:

 :dump void:triples TRIPLES .

Meta fields for link construction in RDF

All meta fields for link construction () except for MESSAGE can be mapped to RDF triples.

The PREFIX meta field () SHOULD be mapped to the RDF property void:uriSpace or void:uriRegexPattern with :sourceset as RDF subject.

The TARGET meta field ( SHOULD be mapped to the RDF property void:uriSpace or void:uriRegexPattern with :targetset as RDF subject.

The RELATION meta field (), if its value contains an URI, SHOULD mapped to the RDF property void:linkPredicate with :dump as RDF subject.

The ANNOTATION meta field () is used to map link annotations to RDF () unless the RELATION meta field contains an URI template.

Meta fields for link dumps in RDF

Meta fields for link dumps () describe properties of the link dump.

The DESCRIPTION meta field () corresponds to the dcterms:description RDF property. For instance

#DESCRIPTION: Mapping from ids to documents

can be mapped to

:dump dcterms:description "Mapping from ids to documents" .

The CREATOR meta field () corresponds to the dcterms:creator RDF property. The RDF object SHOULD NOT be a literal node. For instance

#CREATOR: Bea Beacon

can be mapped to

:dump dcterms:creator [ foaf:name "Bea Beacon" ] .

A field value starting with http:// or https:// is interpreted as URI instead of string. For instance

#CREATOR: http://example.org/people/bea

can be mapped to

:dump dcterms:creator <http://example.org/people/bea> .

The CONTACT meta field () corresponds to the foaf:mbox RDF property. The RDF object SHOULD NOT be a literal node. For instance

 #CONTACT: admin@example.com

can be mapped to

 :dump dcterms:creator [ foaf:mbox <mailto:admin@example.com> ] .

and

 #CONTACT: Bea Beacon <bea@example.org>

can be mapped to

 :dump dcterms:creator [
     foaf:name "Bea Beacon" ;
     foaf:mbox <mailto:bea@example.org>
 ] .

The HOMEPAGE meta field () corresponds to the foaf:homepage RDF property. For instance

#HOMEPAGE: http://example.org/about.html

can be mapped to

:dump foaf:homepage <http://example.org/about.html> .

The FEED meta field () corresponds to the void:dataDump RDF property. For instance

#FEED: http://example.com/beacon.txt

can be mapped to

:dump void:dataDump <http://example.com/beacon.txt> .

The TIMESTAMP meta field () corresponds to the dcterms:modified RDF property. For instance the following valid timestamps

 #TIMESTAMP: 2012-05-30
 #TIMESTAMP: 2012-05-30T15:17:36+02:00
 #TIMESTAMP: 2012-05-30T13:17:36Z

can be mapped to the following RDF triples, respectively:

 :dump dcterms:modified "2012-05-30"^^xsd:date
 :dump dcterms:modified "2012-05-30T15:17:36+02:00"^^xsd:dateTime
 :dump dcterms:modified "2012-05-30T13:17:36Z"^^xsd:dateTime

The UPDATE meta field () corresponds to the rssynd:updatePeriod RDF property. For instance a daily update

#UPDATE: daily

can be mapped to

:dump rssynd:updatePeriod "daily" .

Meta fields for datasets in RDF

Meta fields for the datasets () are mapped to subjects and objects of RDF triples to describe the source dataset and target dataset, respectively.

The SOURCESET meta field () replaces the blank node :sourceset.

The TARGETSET meta field () replaces the blank node :targetset.

The NAME meta field () is mapped to the RDF property dcterms:title with :targetset as RDF subject. For instance the field value "Wikipedia", expressible in BEACON format as

#NAME: Wikipedia

can be mapped to

:targetset dcterms:title "Wikipedia" .

The INSTITUTION meta field () corresponds to the RDF property dcterms:publisher. The RDF object SHOULD NOT be a literal node. For instance

#INSTITUTION: Wikimedia Foundation

can be mapped

:dump dcterms:publisher [ foaf:name "Wikimedia" ] .

A field value starting with http:// or https:// is interpreted as URI instead of string. For instance

#INSTITUTION: http://viaf.org/viaf/137022054/

can be mapped to

:targetset dcterms:publisher http://viaf.org/viaf/137022054/ .

Limitations and applications

BEACON format () can be used as serialization format for RDF graphs where all parts of RDF triples are IRIs and IRIs do not contain the character sequences %7C, %0A, %0D, or any other percent-encoded character not included in the list of allowed characters (). This limitation applies because the disallowed character sequences would need to result from characters not allowed in link tokens of BEACON format.

BEACON link dumps can be served for instance as Triple Pattern Fragments which also consist of a set of links sharing a common pattern, and additional metadata.