Generating RDF collections

[mielvds]

Hi! I was wondering whether SPARQL anything can support the construction of an RDF Collection, eg. in cases where order of a CSV or JSON array needs to be mapped to as rdf:List (like for the object of skos:memberList).

1. Do the functions with container membership properties extend to collections as well, or can they be made that way?
2. Creating a collection is difficult in SPARQL 1.1. Is it possible to add a function that creates a collection, like fx:list(?a, ?l), which adds ?a to a list ?l?

[enridaga]

Thank you, this is an interesting question!

Do the functions with container membership properties extend to collections as well, or can they be made that way?

They only work with container membership properties, querying rdf:List is quite hard in SPARQL (and you don't need to to query Facade-X as collections are represented as containers, like rdf:Seq and not rdf:List). There is no plan at the moment of adding functions for rdf:List. However, you can find something in Apache Jena functions that should work with SPARQL Anything as well: https://jena.apache.org/documentation/query/library-propfunc.html

Personally, I dislike rdf:List as I find it quite hard to work with in comparison to container membership properties. FYI, the query-ability of the different list representations in RDF was analysed in detail in this article: https://content.iospress.com/articles/semantic-web/sw210436

Creating a collection is difficult in SPARQL 1.1. Is it possible to add a function that creates a collection, like fx:list(?a, ?l), which adds ?a to a list ?l?

I am not sure how such a function could work in SPARQL (but see Jena functions for some functions with rdf:List).

However, you don't need any special feature to build RDF Collections with SPARQL, see the following example.

Input data (data.csv):

item-1
item-2
item-3
item-4
item-4
item-6

Query make-list.sparql:

PREFIX owl:  <http://www.w3.org/2002/07/owl#>
PREFIX rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX fx:   <http://sparql.xyz/facade-x/ns/>
PREFIX xyz:  <http://sparql.xyz/facade-x/data/>

CONSTRUCT {
 ?item a rdf:List .
 ?item rdf:first ?value .
 ?item rdf:rest ?rest .
} WHERE {
#SELECT * WHERE {
	SERVICE <x-sparql-anything:> {
		fx:properties fx:location "./data.csv" .
		?csv a fx:root .
		?csv ?li ?item .
		?item rdf:_1 ?value
		OPTIONAL { ?csv ?li2 ?next . filter (fx:next(?li) = ?li2) }
		BIND (IF(BOUND(?next), ?next, rdf:nil) AS ?rest )
	}
}

Output of $ java -jar sparql-anything-0.6.0.jar -q make-list.sparql

@prefix fx:   <http://sparql.xyz/facade-x/ns/> .
@prefix owl:  <http://www.w3.org/2002/07/owl#> .
@prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xyz:  <http://sparql.xyz/facade-x/data/> .

[ rdf:type   rdf:List ;
  rdf:first  "item-1" ;
  rdf:rest   [ rdf:type   rdf:List ;
               rdf:first  "item-2" ;
               rdf:rest   [ rdf:type   rdf:List ;
                            rdf:first  "item-3" ;
                            rdf:rest   [ rdf:type   rdf:List ;
                                         rdf:first  "item-4" ;
                                         rdf:rest   [ rdf:type   rdf:List ;
                                                      rdf:first  "item-4" ;
                                                      rdf:rest   [ rdf:type   rdf:List ;
                                                                   rdf:first  "item-6" ;
                                                                   rdf:rest   ()
                                                                 ]
                                                    ]
                                       ]
                          ]
             ]
] .

[mielvds]

Thanks @enridaga, that query is quite neat and solves the problem! In fact, I think a repository of query templates for common and not so common patterns would be a nice addition of the website or docs. Patterns like that "could" also be captured in functions such as the jena ones for usability sake.

Personally, I dislike rdf:List as I find it quite hard to work with in comparison to container membership properties.

Me neither, but if SKOS tells you it's rdf:List, it's rdf:List :)

[enridaga]

I think a repository of query templates for common and not so common patterns would be a nice addition of the website or docs.

Indeed :)